Add release workflow

.github/workflows/release.yml

@@ -0,0 +1,24 @@
+name: Release
+
+on:
+  release:
+    types: [published]
+
+jobs:
+  release:
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v2
+
+    - name: Update major version tag
+      run: |
+        version=$(echo "${{ github.ref }}" | sed -r "s/^.*(v[0-9]).*$/\1/")
+
+        echo "Major Version: $version"
+
+        git config --local user.email "github-actions"
+        git config --local user.name "[email protected]"
+
+        git tag -fa $version -m "Update $version tag"
+        git push -f origin $version

README.md

@@ -31,3 +31,13 @@ This action follows [the recommendations of GitHub Actions Versioning](https://g
 $ yarn
 $ yarn run package
 ```
+
+## Releasing
+
+1. Check the package contents are up-to-date
+    ```
+    $ yarn run package
+    $ git diff
+    ```
+2. Create new release to publish to the GitHub Marketplace
+3. Make sure that [the release workflow](https://github.com/hidakatsuya/setup-diff-pdf/actions/workflows/release.yml) is successful