ci: enable CHANGELOG validation

Closes: #1478

.github/workflows/changelog-check.yml

@@ -0,0 +1,57 @@
+# From https://github.com/anatawa12/AvatarOptimizer/blob/ccb863243433019f323c23a3a2e24b27e15b2f6c/.github/workflows/changelog-check.yml
+# Copyright 2022 anatawa12
+# MIT license.
+
+# this workflow checks CHANGELOG.md & CHANGELOG-SNAPSHOTS.md is updated correctly
+# to skip this check, include `NO-CHANGELOG` for CHANGELOG.md
+# and `NO-CHANGELOG-PRERELEASE` for CHANGELOG-PRERELEASE.md in tags of PR.
+# also, this action ignores `dependencies` pull requests (expected to be generated by dependabot)
+
+name: CHANGELOG check
+
+on:
+  pull_request_target:
+    branches: [ main, main-* ]
+    types: [ opened, synchronize, reopened, ready_for_review, labeled, unlabeled ]
+
+# A workflow run is made up of one or more jobs that can run sequentially or in parallel
+jobs:
+  releasenote-check:
+    if: ${{ ! github.event.pull_request.draft }}
+    runs-on: ubuntu-latest
+    
+    strategy:
+      matrix:
+        file: [CHANGELOG.md, CHANGELOG-jp.md, CHANGELOG-PRERELEASE.md, CHANGELOG-PRERELEASE-jp.md]
+
+    env:
+      NO_CHANGELOG: ${{
+        contains(github.event.pull_request.labels.*.name, 'NO-CHANGELOG')
+        || contains(github.event.pull_request.labels.*.name, 'documentation')
+        || contains(github.event.pull_request.labels.*.name, 'localization')
+        || contains(github.event.pull_request.labels.*.name, 'ci')
+        || contains(github.event.pull_request.labels.*.name, 'refactor')
+        || '' }}
+      SNAPSHOT_ONLY: ${{ contains(github.event.pull_request.labels.*.name, 'PRERELEASE-ONLY') || '' }}
+    # Steps represent a sequence of tasks that will be executed as part of the job
+    steps:
+      - name: Dump GitHub context
+        env:
+          GITHUB_CONTEXT: ${{ toJson(github) }}
+        run: echo "$GITHUB_CONTEXT"
+      - name: Fetch pull_request info
+        env:
+          GH_REPO: ${{ github.repositoryUrl }}
+          GH_TOKEN: ${{secrets.GITHUB_TOKEN}}
+          PR_NUM: ${{ github.event.number }}
+        run: |
+          gh pr view $PR_NUM --json=files | jq --raw-output '.files[].path' > files.txt
+      - name: Changelog check for ${{ matrix.file }}
+        if: always() && !env.NO_CHANGELOG && (startsWith(matrix.file, 'CHANGELOG-PRERELEASE') || !env.SNAPSHOT_ONLY)
+        run: |
+          if ! grep -e '^${{ matrix.file }}$' < files.txt > /dev/null; then
+            echo "::error::An entry in ${{ matrix.file }} is required for this PR."
+            echo "If this change is only relevant between snapshot versions: Add the label 'PRERELEASE-ONLY' to this PR." >> $GITHUB_STEP_SUMMARY
+            echo "If this change does not warrant any release notes: Add the label 'NO-CHANGELOG' to this PR." >> $GITHUB_STEP_SUMMARY
+            exit 1
+          fi