CI: Migrate from Travis to GitHub Actions

Fixes #5.

.github/workflows/ci.yaml

@@ -0,0 +1,64 @@
+name: CI
+
+on:
+  push:
+    branches: [ "master" ]
+  pull_request:
+    branches: [ "master" ]
+
+# The CACHE_VERSION can be updated to force the use of a new cache if
+# the current cache contents become corrupted/invalid.  This can
+# sometimes happen when (for example) the OS version is changed but
+# older .so files are cached, which can have various effects
+# (e.g. cabal complains it can't find a valid version of the "happy"
+# tool).
+env:
+  CACHE_VERSION: 1
+
+jobs:
+  build:
+    runs-on: ${{ matrix.os }}
+    strategy:
+      matrix:
+        os: [ubuntu-22.04]
+        ghc: ["9.4.8", "9.6.6", "9.8.2"]
+        cabal: ["3.10.3.0"]
+
+    steps:
+    - uses: actions/checkout@v4
+      with:
+        submodules: true
+
+    - uses: haskell-actions/setup@v2
+      id: setup-haskell
+      with:
+        ghc-version: ${{ matrix.ghc }}
+        cabal-version: ${{ matrix.cabal }}
+
+    - uses: actions/cache/restore@v4
+      name: Restore cabal store cache
+      with:
+        path: |
+          ${{ steps.setup-haskell.outputs.cabal-store }}
+          dist-newstyle
+        key: ${{ env.CACHE_VERSION }}-cabal-${{ matrix.os }}-${{ matrix.ghc }}-${{ hashFiles(format('cabal.GHC-{0}.config', matrix.ghc)) }}-${{ github.sha }}
+        restore-keys: |
+          ${{ env.CACHE_VERSION }}-cabal-${{ matrix.os }}-${{ matrix.ghc }}-${{ hashFiles(format('cabal.GHC-{0}.config', matrix.ghc)) }}-
+
+    - name: Update
+      run: cabal update
+    - name: Configure
+      run: cabal configure --enable-tests
+    - name: Build
+      run: cabal build
+    - name: Run tests
+      run: cabal test
+
+    - uses: actions/cache/save@v4
+      name: Save cabal store cache
+      if: always()
+      with:
+        path: |
+          ${{ steps.setup-haskell.outputs.cabal-store }}
+          dist-newstyle
+        key: ${{ env.CACHE_VERSION }}-cabal-${{ matrix.os }}-${{ matrix.ghc }}-${{ hashFiles(format('cabal.GHC-{0}.config', matrix.ghc)) }}-${{ github.sha }}