Add action to build docker image.

.github/workflows/dh.yml

@@ -0,0 +1,32 @@
+name: Build a docker image
+
+on:
+  push:
+    branches:
+    - docker-test
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Check out code
+        uses: actions/checkout@v3
+      - name: Set up Java 
+        uses: actions/setup-java@v2
+        with:
+          distribution: temurin
+          java-version: 17
+          cache: maven
+      - name: Build with Maven
+        run: mvn clean install
+      - name: Setup Docker Buildx
+        uses: docker/setup-buildx-action@v2
+        with:
+          driver: docker
+      - name: Build docker
+        uses: docker/build-push-action@v2
+        with:
+          context: ./
+          load: true
+          tags: |
+            jitsi/jitsi-multitrack-recorder:latest