GH Actions: install gpg key similar to other spring projects

.github/workflows/eclipse-ls-extensions.yml

@@ -29,6 +29,12 @@ jobs:
         run: |
           cd headless-services
           xvfb-run mvn --batch-mode clean install -DskipTests
+      - name: Install GPG key
+        run: |
+          mkdir ~/gpg-keyring
+          cd gpg-keyring
+          echo "${{ secrets.GPG_PRIVATE_KEY }}" > gpg.asc
+          echo "${{ secrets.GPG_PASSPHRASE }}" | gpg --batch --yes --passphrase-fd 0 --import gpg.asc
       - name: Build Eclipse LS extensions
         env:
           tools_s3_access_key: ${{ secrets.TOOLS_S3_ACCESS_KEY }}