chore: fix type error in lib (#218)

Author: ota-meshi

.github/workflows/NodeCI.yml

@@ -16,6 +16,8 @@ jobs:
         run: yarn install
       - name: Lint
         run: yarn lint
+      - name: Build
+        run: yarn build
   test:
     runs-on: ubuntu-latest
     strategy:

tsconfig.json

@@ -10,7 +10,9 @@
     "noFallthroughCasesInSwitch": true,
     "noUnusedLocals": true,
     "noUnusedParameters": true,
-    "esModuleInterop": true
+    "esModuleInterop": true,
+
+    "skipLibCheck": true
   },
   "include": [
     "src/**/*.ts",