Install flatpak-builder on runner before Maven build

Author: Lane Anderson

.github/workflows/build-and-package.yml

@@ -24,6 +24,11 @@ jobs:
         distribution: 'temurin'
         java-version: '25'
 
+    - name: Install flatpak-builder
+      run: |
+        sudo apt-get update
+        sudo apt-get install -y flatpak-builder
+
     - name: Build with Maven
       run: mvn clean install