Flatpak: Add screenshots

.github/workflows/linux_build_flatpak.yml

@@ -83,8 +83,14 @@ jobs:
           arch: x86_64
           build-bundle: true
           verbose: true
+          mirror-screenshots-url: https://dl.flathub.org/repo/screenshots
+          branch: stable
           cache: true
           restore-cache: true
           cache-key: ${{ inputs.os }} ${{ inputs.platform }} ${{ inputs.compiler }} ${{ inputs.detail }} flatpak ${{ hashFiles('.github/workflows/scripts/linux/flatpak/**/*.json') }}
 
+      - name: Commit screenshots to OSTree
+        run: |
+          ostree commit --repo=repo --canonical-permissions --branch=screenshots/x86_64 .github/workflows/scripts/linux/flatpak/screenshots
+
       # TODO: Push to flathub

.github/workflows/scripts/linux/pcsx2-qt.metainfo.xml.in

@@ -13,6 +13,14 @@
   </description>
   <url type="homepage">https://pcsx2.net/</url>
   <url type="bugtracker">https://github.com/PCSX2/pcsx2/issues</url>
+  <screenshots>
+    <screenshot type="default">
+      <image>https://raw.githubusercontent.com/PCSX2/pcsx2/master/.github/workflows/scripts/linux/flatpak/screenshots/screenshot1.png</image>
+    </screenshot>
+    <screenshot>
+      <image>https://raw.githubusercontent.com/PCSX2/pcsx2/master/.github/workflows/scripts/linux/flatpak/screenshots/screenshot2.png</image>
+    </screenshot>
+  </screenshots>
   <content_rating type="oars-1.1"/>
   <update_contact>pcsx2_AT_pcsx2.net</update_contact>
   <releases>