ci: configure GitHub Actions to package code

Packaging code includes testing code.
Code will be packaged when for pull request to `main` and commits on `main`.

This should ensure fully working code on `main`.

Author: odzhychko

.github/workflows/package.yml

@@ -0,0 +1,28 @@
+name: Package
+
+on:
+  push:
+    branches: [ "main" ]
+  pull_request:
+    branches: [ "main" ]
+
+jobs:
+  build:
+
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v4
+      - name: Set up JDK 21
+        uses: actions/setup-java@v4
+        with:
+          # Compile source and target are still specified in pom.xml
+          java-version: '21'
+          distribution: 'temurin'
+          cache: maven
+      - name: Build with Maven
+        run: mvn --batch-mode package
+
+      # Optional: Uploads the full dependency graph to GitHub to improve the quality of Dependabot alerts this repository can receive
+      - name: Update dependency graph
+        uses: advanced-security/maven-dependency-submission-action@v4