Add changelog linting to GitHub CI

Author: neilmayhew

.github/workflows/haskell.yml

@@ -645,3 +645,26 @@ jobs:
           echo 'The diff must not contain any `undefined` values'
           false
         fi
+
+  changelog-lint:
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v4
+
+    - name: Install changelog linter
+      run: |
+        cd "$(mktemp -d)"
+        cat <<EOF >cabal.project
+        source-repository-package
+          type: git
+          location: https://github.com/neilmayhew/changelogs.git
+          tag: 8a1029b8e67b534fe918477275026e1a38c5053c
+        EOF
+        cabal update
+        cabal install changelogs
+
+    - name: Run linter
+      run: |
+        git ls-files '*/CHANGELOG.md' | grep -ve -spec/ | xargs -r changelogs --inplace
+        git diff