Migrate to GitHub Actions from Travis CI.

.github/workflows/scala.yml

@@ -0,0 +1,34 @@
+# This workflow uses actions that are not certified by GitHub.
+# They are provided by a third-party and are governed by
+# separate terms of service, privacy policy, and support
+# documentation.
+
+name: Scala CI
+
+on:
+  push:
+    branches: [ "main" ]
+  pull_request:
+    branches: [ "main" ]
+
+permissions:
+  contents: read
+
+jobs:
+  build:
+
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v4
+    - name: Set up JDK 11
+      uses: actions/setup-java@v4
+      with:
+        java-version: '11'
+        distribution: 'temurin'
+        cache: 'sbt'
+    - uses: sbt/setup-sbt@v1
+    - name: Run formatting check
+      run: sbt scalafmtCheckAll
+    - name: Run tests
+      run: sbt +test