Add github actions workflow (rat)

.github/workflows/rat.yml

@@ -0,0 +1,23 @@
+name: rat
+on:
+  push:
+  pull_request:
+    branches:
+      - master
+      - branch-*
+    types: [opened, synchronize]
+
+jobs:
+  license-check:
+    runs-on: ubuntu-18.04
+    env:
+      MAVEN_OPTS: "-Dorg.slf4j.simpleLogger.log.org.apache.maven.cli.transfer.Slf4jMavenTransferListener=warn"
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v2
+      - name: Set up JDK 8
+        uses: actions/setup-java@v1
+        with:
+          java-version: 8
+      - name: Check Rat
+        run: mvn apache-rat:check -Prat -B

pom.xml

@@ -1705,7 +1705,7 @@
               <exclude>**/.idea/</exclude>
               <exclude>**/*.iml</exclude>
               <exclude>.git/</exclude>
-              <exclude>.github/*</exclude>
+              <exclude>.github/</exclude>
               <exclude>.gitignore</exclude>
               <exclude>git.properties</exclude>
               <exclude>.repository/</exclude>