SOLR-14856: Adding docker test to github workflow. (#1859)

.github/workflows/docker-test.yml

@@ -0,0 +1,32 @@
+name: Docker Build & Test
+
+on:
+  pull_request:
+    branches:
+      - 'master'
+    paths:
+      - '.github/workflows/docker-test.yml'
+      - 'solr/bin/**'
+      - 'solr/contrib/prometheus-exporter/bin/**'
+      - 'solr/docker/**'
+      - 'solr/packaging/**'
+
+jobs:
+  test:
+    name: Build and test Docker image
+
+    runs-on: ubuntu-latest
+
+    steps:
+    # Setup
+    - uses: actions/checkout@v2
+    - name: Set up JDK 11
+      uses: actions/setup-java@v1
+      with:
+        java-version: 11
+    - name: Grant execute permission for gradlew
+      run: chmod +x gradlew
+    - name: Build Docker image with Gradle
+      run: ./gradlew solr:docker:docker
+    - name: Run tests on Docker image
+      run: ./gradlew solr:docker:testDocker