WORKFLOW: added appdata validation step on main [skip ci]

.github/workflows/main-selfhosted.yml

@@ -53,7 +53,10 @@ jobs:
       - name: Check versions (main only)
         id: check_version_string
         run: "automation_tools/main_version_checker.sh"
-        continue-on-error: true
+
+      - name: Check versions (main only)
+        id: check_version_string
+        run: "automation_tools/manifest-validation.sh"
 
       - name: "[DEBUG] Outputting manifest"
         run: cat net.retrodeck.retrodeck.yml

automation_tools/manifest-validation.sh

@@ -0,0 +1,5 @@
+#!/bin/bash
+
+flatpak install -y flathub org.flatpak.Builder
+
+flatpak run --command=appstream-util org.flatpak.Builder validate -v net.retrodeck.retrodeck.appdata.xml