Create release-plugin.yml

add git action to automatically release the plugin to gradle plugin portal.

.github/workflows/release-plugin.yml

@@ -0,0 +1,30 @@
+# This workflow will build a Java project with Gradle
+# For more information see: https://help.github.com/actions/language-and-framework-guides/building-and-testing-java-with-gradle
+
+name: Release plugin to gradle portal
+
+on:
+  release:
+    branches: [ master ]
+
+jobs:
+  relase:
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v2
+    - name: Set up JDK 1.8
+      uses: actions/setup-java@v1
+      with:
+        java-version: 1.8
+    - name: Grant execute permission for gradlew
+      run: chmod +x gradlew
+    - name: test
+      run: ./gradlew test
+    - name: set API keys
+      run: |
+        mkdir -p ~/.gradle
+        echo "gradle.publish.key=${{secrets.GRADLE_PUBLISH_KEY}}" > ~/.gradle/gradle.properties
+        echo "gradle.publish.secret=${{secrets.GRADLE_PUBLISH_SECRET}}" > ~/.gradle/gradle.properties
+    - name: publish plugins
+      run: ./gradlew publishPlugins