CI: Add ghc 9.12 to the build matrix

Author: erikd

.github/workflows/ci.yml

@@ -13,7 +13,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        ghc: ["8.10", "9.0", "9.2", "9.4", "9.6", "9.8", "9.10"]
+        ghc: ["8.10", "9.0", "9.2", "9.4", "9.6", "9.8", "9.10", "9.12"]
     steps:
       - uses: actions/checkout@v4
       - name: "Setup haskell"