Add ro access to steam flatpak install folder

This is required since #72 to verify Steam installation type

Author: Eskander

.flatpak/com.steamgriddb.SGDBoop.yml

@@ -28,6 +28,8 @@ finish-args:
   - --filesystem=~/.var/app/com.valvesoftware.Steam/data/Steam/appcache/librarycache:rw
   - --filesystem=~/.var/app/com.valvesoftware.Steam/data/registry.vdf:ro
   - --filesystem=~/.var/app/com.valvesoftware.Steam:rw
+  # For checking Steam installation type
+  - --filesystem=/var/lib/flatpak/app/com.valvesoftware.Steam:ro
 modules:
   - name: sgdboop
     no-autogen: true