Migrate the CI to GitHub Actions.

Author: sjrd

.github/workflows/ci.yml

@@ -0,0 +1,31 @@
+name: CI
+on:
+  push:
+    branches:
+      - master
+  pull_request:
+    branches:
+      - master
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        scalaversion: ["2.11.12", "2.12.13", "2.13.4"]
+        platform: ["JVM", "JS", "JS-0.6.x", "Native"]
+    env:
+      SCALAJS_VERSION: "${{ matrix.platform == 'JS-0.6.x' && '0.6.33' || '' }}"
+      PROJECT_NAME: "portable-scala-reflect${{ matrix.platform == 'JS-0.6.x' && 'JS' || matrix.platform }}"
+    steps:
+      - uses: actions/checkout@v2
+      - uses: olafurpg/setup-scala@v10
+        with:
+          java-version: "adopt@1.8"
+      - uses: coursier/cache-action@v5
+      - name: Unit tests
+        run: sbt "++${{ matrix.scalaversion }}" "${{ env.PROJECT_NAME }}/test"
+      - name: Test generate documentation
+        run: sbt "++${{ matrix.scalaversion }}" "${{ env.PROJECT_NAME }}/doc"
+      - name: MiMa
+        run: sbt "++${{ matrix.scalaversion }}" "${{ env.PROJECT_NAME }}/mimaReportBinaryIssues"