ci: Add actions to write to changelog.entries on each merged PRs

Author: donmor

.github/changelog.entries

@@ -0,0 +1,40 @@
+name: Update changelog on PR merge
+
+on:
+  pull_request:
+    types: [closed]
+    branches:
+      - master
+
+jobs:
+  update:
+    if: github.event.pull_request.merged == true
+    runs-on: ubuntu-latest
+  permissions:
+    contents: write
+    pull-requests: read
+  steps:
+    - id: check-title
+      run: |
+        PR_TITLE="${{ github.event.pull_request.title }}"
+        PR_NUMBER=${{ github.event.pull_request.number }}
+        PR_AUTHOR=${{ github.event.pull_request.user.login }}
+        ALLOWED_PREFIXES="^(core|desktop|web|avm1|avm2|docs|chore|tests): " # more tags here
+        if [[ ! "$PR_TITLE" =~ $ALLOWED_PREFIXES ]]; then
+          echo "skip_collect=true" >> $GITHUB_OUTPUT
+          exit 0
+        fi
+        echo "entry=$PR_TITLE" >> $GITHUB_OUTPUT
+        echo "number=$PR_NUMBER" >> $GITHUB_OUTPUT
+        echo "author=$PR_AUTHOR" >> $GITHUB_OUTPUT
+    - name: Checkout repository, write to first line and push
+      if: steps.check-title.outputs.skip_collect != 'true'
+      uses: actions/checkout@v6
+      run: |
+        touch .github/changelog.entries
+        sed -i "1i ${{ steps.check-title.outputs.entry }} by ${{ steps.check-title.outputs.author }} in #${{ steps.check-title.outputs.number }}" .github/changelog.entries
+        git config user.name "github-actions[bot]"
+        git config user.email "41898282+github-actions[bot]@users.noreply.github.com"
+        git add .github/changelog.entries
+        git commit -m "ci: update changelog.entries"
+        git push