ENH: Add "commit-message" GitHub Actions workflow

Adapted from Slicer/Slicer@f39e06f0d

This replaces the usage of https://github.com/marketplace/commitcheck which
has been unreliable at times and also difficult to see what is required to pass
a failing check.

This adds the "Check Commit Prefix" workflow step based on content
available at https://slicer.readthedocs.io/en/latest/developer_guide/style_guide.html#commits.

Co-authored-by: James Butler <james.butler@perkinelmer.com>

.github/workflows/commit-message.yml

@@ -0,0 +1,36 @@
+name: 'Commit Message Check'
+on:
+  pull_request:
+    types:
+      - opened
+      - edited
+      - reopened
+      - synchronize
+  push:
+    branches:
+      - main
+
+jobs:
+  check-commit-message:
+    name: Check Commit Message
+    runs-on: ubuntu-latest
+    steps:
+      - name: Check Commit Prefix
+        uses: gsactions/commit-message-checker@16fa2d5de096ae0d35626443bcd24f1e756cafee # v2.0.0
+        with:
+          pattern: '^(ENH|PERF|BUG|STYLE|DOC|COMP): ([A-Z])+'
+          flags: 'gm'
+          excludeDescription: 'true' # optional: this excludes the description body of a pull request
+          excludeTitle: 'true' # optional: this excludes the title of a pull request
+          error: 'The first line has to start with a commit prefix, followed by a colon and space, and then followed by a message with a capital letter (e.g "ENH: Add support for awesome feature"). For more details on other requirements, see https://slicer.readthedocs.io/en/latest/developer_guide/style_guide.html#commits'
+          checkAllCommitMessages: 'true' # optional: this checks all commits associated with a pull request
+          accessToken: ${{ secrets.GITHUB_TOKEN }} # github access token is only required if checkAllCommitMessages is true
+      - name: Check Line Length
+        uses: gsactions/commit-message-checker@16fa2d5de096ae0d35626443bcd24f1e756cafee # v2.0.0
+        with:
+          pattern: '^[^#].{1,78}$'
+          error: 'The maximum line length of 78 characters is exceeded. For more details, see https://slicer.readthedocs.io/en/latest/developer_guide/style_guide.html#commits'
+          excludeDescription: 'true' # optional: this excludes the description body of a pull request
+          excludeTitle: 'true' # optional: this excludes the title of a pull request
+          checkAllCommitMessages: 'true' # optional: this checks all commits associated with a pull request
+          accessToken: ${{ secrets.GITHUB_TOKEN }} # github access token is only required if checkAllCommitMessages is true