Add tests section to labeler config

Author: ciarams87

.github/labeler.yml

@@ -20,3 +20,6 @@ documentation:
 dependencies:
   - head-branch: ['^deps/', '^dep/', '^dependabot/', 'pre-commit-ci-update-config']
   - changed-files: ['go.mod', 'go.sum']
+
+tests:
+  - head-branch: ['^test/', '^tests/']