adds plugin verifier workflow

.github/workflows/plugin-verifier.yaml

@@ -0,0 +1,21 @@
+name: Plugin compatibility
+on:
+  - push
+  - workflow_dispatch
+jobs:
+  run:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@master
+      - name: Setup Java
+        uses: actions/setup-java@v1
+        with:
+          java-version: 11.x.x
+      - name: Build the plugin using Gradle
+        run: ./gradlew buildPlugin
+      - uses: thepieterdc/intellij-plugin-verifier-action@v1.3.0
+        with:
+          plugin: 'build/distributions/couchbase-intellij-plugin-*'
+          verifier_version: 1.301
+          versions: |
+            LATEST-EAP-SNAPSHOT