chore: bump default node version and flarum/action-build

Author: DavideIadeluca

.github/workflows/REUSABLE_frontend.yml

@@ -74,7 +74,7 @@ on:
         description: The node version to use for the workflow.
         type: number
         required: false
-        default: 16
+        default: 20
 
       js_package_manager:
         description: "Enable TypeScript?"
@@ -142,7 +142,7 @@ jobs:
         working-directory: ${{ inputs.frontend_directory }}
 
       - name: JS Checks & Production Build
-        uses: flarum/action-build@v3
+        uses: flarum/action-build@v4
         with:
           github_token: ${{ secrets.GITHUB_TOKEN }}
           build_script: ${{ inputs.build_script }}