chore(manifest): add --filesystem=host permission

Because ezthumb is built using GTK 2, the Flatpak portal for file access
isn't available, which greatly limits the usability of the app.

By allowing the app unrestricted access to the entire filesystem, we
make it much more useful for the average person who doesn't know how to
handle Flatpak permissions.

Power users concerned with the security implications of this, can always
go back to how it was with the following command:

flatpak --user override --nofilesystem=host --persist=.config/ezthumb --filesystem=xdg-videos io.sourceforge.ezthumb

Author: guihkx

io.sourceforge.ezthumb.yaml

@@ -7,8 +7,7 @@ command: ezthumb
 finish-args:
   - --share=ipc
   - --socket=x11
-  - --filesystem=xdg-videos
-  - --persist=.config/ezthumb
+  - --filesystem=host
 
 cleanup:
   - /include