Add GHC 9.12 to CI

Author: alexfmpe

.github/workflows/haskell.yml

@@ -6,7 +6,7 @@ jobs:
   build:
     strategy:
       matrix:
-        ghc: ['8.6', '8.8', '8.10', '9.0', '9.2', '9.4', '9.6', '9.8', '9.10']
+        ghc: ['8.6', '8.8', '8.10', '9.0', '9.2', '9.4', '9.6', '9.8', '9.10', '9.12']
         os: ['ubuntu-latest', 'macos-latest']
     runs-on: ${{ matrix.os }}