Adds gpg private key (#9)

Author: StrongestNumber9

.github/workflows/release.yaml

@@ -21,6 +21,8 @@ jobs:
         distribution: 'temurin'
         server-id: github
         settings-path: ${{ github.workspace }}
+        gpg-private-key: ${{ secrets.MAVEN_GPG_PRIVATE_KEY }}
+        gpg-passphrase: MAVEN_GPG_PASSPHRASE
 
     - name: Publish to GitHub Packages
       run: mvn --batch-mode -Drevision=${{ github.event.release.tag_name }} -Dsha1= -Dchangelist= clean deploy -Ppublish-github-packages