Create release script to publish jar on tag push

This commit adds a new github workflow to the project which is
responsible for building and publishing the final serena jar to the
github releases when a commit has been tagged.

.github/workflows/release.yml

@@ -0,0 +1,30 @@
+name: release-project
+
+on: push
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v1
+        if: startsWith(github.ref, 'refs/tags/')
+
+      - name: Set up JDK 1.12
+        uses: actions/setup-java@v1
+        if: startsWith(github.ref, 'refs/tags/')
+        with:
+          java-version: 1.12
+
+
+      - name: Build with Maven
+        run: mvn -B package --file pom.xml -Djar.finalName=serena
+        if: startsWith(github.ref, 'refs/tags/')
+
+      - name: Release
+        uses: softprops/action-gh-release@v1
+        if: startsWith(github.ref, 'refs/tags/')
+        with:
+          files: target/serena.jar
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}