feat: push docker image on push to main

.github/workflows/cr-main.yml

@@ -0,0 +1,36 @@
+name: Master Branch Continuous Release
+
+on:
+  push:
+    branches:
+      - master
+
+env:
+  REGISTRY_IMAGE: inspectit/inspectit-gepard-agent
+
+jobs:
+  build-jar:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - name: Set up JDK 21
+        uses: actions/setup-java@v4
+        with:
+          java-version: '21'
+          distribution: 'temurin'
+
+      - name: Setup Gradle
+        uses: gradle/actions/setup-gradle@417ae3ccd767c252f5661f1ace9f835f9654f2b5 # v3.1.0
+        with:
+          build-scan-publish: true
+          build-scan-terms-of-service-url: "https://gradle.com/terms-of-service"
+          build-scan-terms-of-service-agree: "yes"
+
+      - name: Build with Gradle
+        run: ./gradlew build
+
+      - name: Upload artifact
+        uses: actions/upload-artifact@v3
+        with:
+          name: agent-artifact
+          path: backend/build/libs/backend-0.0.1-SNAPSHOT.jar