ci: Add release GitHub workflow

Using a "custom" way to create a releasing with multiple artifacts following this issue:
- actions/upload-release-asset#28 (comment)
- https://github.com/hashicorp/terraform-provider-kubernetes-alpha/blob/6a94abdffa085bb3564fc3670979cd223045dd5b/.github/workflows/release_binaries.yaml

.github/workflows/release.yml

@@ -0,0 +1,56 @@
+name: Publish release
+on:
+  push:
+    tags:
+      - "[0-9]+.[0-9]+*"
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - name: Setup java
+        uses: actions/setup-java@v1.4.1
+        with:
+          java-version: 1.8
+      - name: Check version not snapshot
+        run: |
+          PROJECT_VERSION=$(./gradlew -q printVersion | tail -n 1)
+          echo "Project version is $PROJECT_VERSION"
+          if [[ "$PROJECT_VERSION" == *"SNAPSHOT" ]]; then exit 1; fi
+      - name: Decrypt large secret
+        run: |
+          chmod +x ./.github/workflows/decrypt_secret.sh
+          ./.github/workflows/decrypt_secret.sh
+        env:
+          GPG_PASSPHRASE: ${{ secrets.GPG_PASSPHRASE }}
+      - name: Build
+        run: ./gradlew build
+      - name: Publish
+        run: ./gradlew publish -PossrhUrl="$PUBLISH_RELEASE_REPO_URL" -PossrhUsername="$PUBLISH_REPO_USERNAME" -PossrhPassword="$PUBLISH_REPO_PASSWORD" -Psigning.keyId="$GPG_KEY_ID" -Psigning.password="$GPG_PASSPHRASE" -Psigning.secretKeyRingFile="$SIGN_FILE_PATH"
+        env:
+          PUBLISH_RELEASE_REPO_URL: https://oss.sonatype.org/service/local/staging/deploy/maven2/
+          PUBLISH_REPO_USERNAME: ${{ secrets.PUBLISH_REPO_USERNAME }}
+          PUBLISH_REPO_PASSWORD: ${{ secrets.PUBLISH_REPO_PASSWORD }}
+          GPG_KEY_ID: ${{ secrets.GPG_KEY_ID }}
+          GPG_PASSPHRASE: ${{ secrets.GPG_PASSPHRASE }}
+          SIGN_FILE_PATH: "${{ github.workspace }}/.github/workflows/jcv_sign.gpg"
+      - name: Create Github release
+        run: |
+          set -x
+          assets=()
+          for asset in ${JCV_CORE_ASSETS_FOLDER}; do
+            assets+=("-a" "$asset")
+          done
+          for asset in ${JCV_ASSERTJ_ASSETS_FOLDER}; do
+            assets+=("-a" "$asset")
+          done
+          for asset in ${JCV_HAMCREST_ASSETS_FOLDER}; do
+            assets+=("-a" "$asset")
+          done
+          hub release create --draft "${assets[@]}" -m "Release of ${{ github.ref }}" "${{ github.ref }}"
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          JCV_CORE_ASSETS_FOLDER: "${{ github.workspace }}/jcv-core/build/libs/*"
+          JCV_ASSERTJ_ASSETS_FOLDER: "${{ github.workspace }}/jcv-assertj/build/libs/*"
+          JCV_HAMCREST_ASSETS_FOLDER: "${{ github.workspace }}/jcv-hamcrest/build/libs/*"