Add template workflow to check for missed updates to Markdown ToC

On every push or pull request that affects the Markdown files of the repository which have generated table of contents,
check whether the table of contents matches the content.

Author: per1234

workflow-templates/assets/check-toc-task/Taskfile.yml

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+# See: https://taskfile.dev/#/usage
+version: "3"
+
+tasks:
+  # Source: https://github.com/arduino/tooling-project-assets/blob/main/workflow-templates/assets/check-toc-task/Taskfile.yml
+  markdown:toc:
+    desc: Update the table of contents
+    cmds:
+      - |
+        npx markdown-toc \
+            --bullets=- \
+            --maxdepth={{.MAX_DEPTH}} \
+            -i \
+            "{{.FILE_PATH}}"

workflow-templates/check-toc-task.md

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+# "Check ToC" workflow (Task)
+
+Workflow file: [check-toc-task.yml](check-toc-task.yml)
+
+Check whether the generated table of contents in Markdown files matches their heading structure.
+
+This should be used in repositories that generate the table of contents with [markdown-toc](https://github.com/jonschlinkert/markdown-toc).
+
+This is the version of the workflow for projects using the [Task](https://taskfile.dev/#/) task runner tool.
+
+## Assets
+
+- [`Taskfile.yml`](assets/check-toc-task/Taskfile.yml] - Formatting task.
+  - Install to: repository root (or add the `markdown:toc` task into the existing `Taskfile.yml`)
+
+## Readme badge
+
+Markdown badge:
+
+```markdown
+[![Check ToC status](https://github.com/REPO_OWNER/REPO_NAME/actions/workflows/check-toc-task.yml/badge.svg)](https://github.com/REPO_OWNER/REPO_NAME/actions/workflows/check-toc-task.yml)
+```
+
+Replace the `REPO_OWNER` and `REPO_NAME` placeholders in the URLs with the final repository owner and name ([example](https://raw.githubusercontent.com/arduino-libraries/ArduinoIoTCloud/master/README.md)).
+
+---
+
+Asciidoc badge:
+
+```adoc
+image:https://github.com/{repository-owner}/{repository-name}/actions/workflows/check-toc-task.yml/badge.svg["Check ToC status", link="https://github.com/{repository-owner}/{repository-name}/actions/workflows/check-toc-task.yml"]
+```
+
+Define the `{repository-owner}` and `{repository-name}` attributes and use them throughout the readme ([example](https://raw.githubusercontent.com/arduino-libraries/WiFiNINA/master/README.adoc)).
+
+## Commit message
+
+```
+Add CI workflow to check for missed updates to readme ToC
+
+On every push or pull request that affects the repository's README.md, check whether the table of contents matches the
+content.
+```
+
+## PR message
+
+```markdown
+On every push or pull request that affects the repository's README.md, use [markdown-toc](https://github.com/jonschlinkert/markdown-toc) to check whether the table of contents matches the content.
+```

workflow-templates/check-toc-task.yml

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+# Source: https://github.com/arduino/.github/blob/master/workflow-templates/check-toc-task.md
+name: Check ToC
+
+# See: https://docs.github.com/en/actions/reference/events-that-trigger-workflows
+on:
+  push:
+    paths:
+      - ".github/workflows/check-toc-task.ya?ml"
+      # TODO: Update this if ToC of any other files should be checked.
+      - "README.md"
+  pull_request:
+    paths:
+      - ".github/workflows/check-toc-task.ya?ml"
+      # TODO: Update this if ToC of any other files should be checked.
+      - "README.md"
+  workflow_dispatch:
+  repository_dispatch:
+
+jobs:
+  check:
+    name: ${{ matrix.file.name }}
+    runs-on: ubuntu-latest
+
+    strategy:
+      fail-fast: false
+
+      matrix:
+        file:
+          # TODO: Update this if any other files should be checked.
+          - name: README.md
+            # Max ToC depth, for use with the markdown-toc --maxdepth flag.
+            maxdepth: 3
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v2
+
+      - name: Install Task
+        uses: arduino/setup-task@v1
+        with:
+          repo-token: ${{ secrets.GITHUB_TOKEN }}
+          version: 3.x
+
+      - name: Rebuild ToC
+        run: |
+          task markdown:toc \
+            FILE_PATH="${{ github.workspace }}/${{ matrix.file.name }}" \
+            MAX_DEPTH=${{ matrix.file.maxdepth }}
+
+      - name: Check ToC
+        run: git diff --color --exit-code

workflow-templates/dependabot/workflow-template-copies/.github/workflows/check-toc-task.yml

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+# Source: https://github.com/arduino/.github/blob/master/workflow-templates/check-toc-task.md
+name: Check ToC
+
+# See: https://docs.github.com/en/actions/reference/events-that-trigger-workflows
+on:
+  push:
+    paths:
+      - ".github/workflows/check-toc-task.ya?ml"
+      # TODO: Update this if ToC of any other files should be checked.
+      - "README.md"
+  pull_request:
+    paths:
+      - ".github/workflows/check-toc-task.ya?ml"
+      # TODO: Update this if ToC of any other files should be checked.
+      - "README.md"
+  workflow_dispatch:
+  repository_dispatch:
+
+jobs:
+  check:
+    name: ${{ matrix.file.name }}
+    runs-on: ubuntu-latest
+
+    strategy:
+      fail-fast: false
+
+      matrix:
+        file:
+          # TODO: Update this if any other files should be checked.
+          - name: README.md
+            # Max ToC depth, for use with the markdown-toc --maxdepth flag.
+            maxdepth: 3
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v2
+
+      - name: Install Task
+        uses: arduino/setup-task@v1
+        with:
+          repo-token: ${{ secrets.GITHUB_TOKEN }}
+          version: 3.x
+
+      - name: Rebuild ToC
+        run: |
+          task markdown:toc \
+            FILE_PATH="${{ github.workspace }}/${{ matrix.file.name }}" \
+            MAX_DEPTH=${{ matrix.file.maxdepth }}
+
+      - name: Check ToC
+        run: git diff --color --exit-code