CI: Add hlint action

Now that hlint runs through cleanly, there is no reason not to.

Related: xmonad/xmonad-contrib@dd26fcc

.github/workflows/hlint.yml

@@ -0,0 +1,23 @@
+# Source: https://github.com/xmonad/xmonad-contrib/blob/e2ffa533da76e6375179eff942bb0647dd22fb58/.github/workflows/hlint.yaml
+name: hlint
+
+on:
+ push:
+ pull_request:
+
+jobs:
+ hlint:
+ runs-on: ubuntu-latest
+ steps:
+ - uses: actions/checkout@v3
+
+ - name: 'Set up HLint'
+ uses: haskell/actions/hlint-setup@v2
+ with:
+ version: '3.5'
+
+ - name: 'Run HLint'
+ uses: haskell/actions/hlint-run@v2
+ with:
+ path: '["src/", "test/", "app/"]'
+ fail-on: status