CI: Run appstreamcli validate

.github/workflows/main.yml

@@ -0,0 +1,20 @@
+name: CI
+on:
+  push:
+  # Allows you to run this workflow manually from the Actions tab
+  workflow_dispatch:
+
+jobs:
+  appstream-validate:
+    runs-on: ubuntu-24.04
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Install appstream
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y appstream
+
+      - name: Validate metainfo
+        run: |
+          appstreamcli validate --strict --pedantic --explain org.DolphinEmu.dolphin-emu.metainfo.xml