Add minimal CI

Author: samtay

.github/workflows/ci.yaml

@@ -0,0 +1,12 @@
+on: [push]
+name: build
+jobs:
+  runhaskell:
+    name: Hello World
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+      - uses: haskell/actions/setup@v2
+        with:
+          enable-stack: true
+      - run: stack build