Worklflow: update copyright monthly

.github/workflows/update-copyright.yml

@@ -0,0 +1,57 @@
+name: Update Copyright
+
+on:
+  # Run automatically every month.
+  schedule:
+    - cron: '0 0 1 * *'
+  workflow_call:
+  # Allow manually triggering the workflow.
+  workflow_dispatch:
+
+jobs:
+  update_copyright:
+    name: Update Copyright
+    runs-on: [ubuntu-latest]
+
+    steps:
+      - name: Setup PHP
+        uses: shivammathur/setup-php@v2
+        with:
+          php-version: 7.4
+
+      - name: Checkout code
+        uses: actions/checkout@v4
+        with:
+          ref: main
+          fetch-depth: 0
+
+      - name: Get composer cache directory
+        id: composer-cache
+        run: echo "dir=$(composer config cache-files-dir)" >> $GITHUB_OUTPUT
+
+      - name: Cache dependencies
+        uses: actions/cache@v4
+        with:
+          path: ${{ steps.composer-cache.outputs.dir }}
+          key: ${{ runner.os }}-composer-${{ hashFiles('**/composer.lock') }}
+          restore-keys: ${{ runner.os }}-composer-
+
+      - name: Install dependencies
+        run: composer install --prefer-dist --no-progress --ignore-platform-req=ext-*
+
+      - name: Update Copyright
+        run: php -f shell/update-copyright.php
+
+      - name: Create Pull Request
+        uses: peter-evans/create-pull-request@v6
+        with:
+          commit-message: update copyright
+          title: Update Copyright
+          body: |
+            - Update copyright
+
+            Auto-generated by [openmage/dev-copyright][1]
+
+            [1]: https://github.com/OpenMage/dev-copyright
+          branch: update-copyright
+          base: main