Add configurable Google Drive toggle in the Documents admin section along with necessary config scaffolding

src/lib/stores/index.ts

@@ -176,6 +176,7 @@ type Config = {
 		enable_signup: boolean;
 		enable_login_form: boolean;
 		enable_web_search?: boolean;
+		enable_google_drive: boolean;
 		enable_image_generation: boolean;
 		enable_admin_export: boolean;
 		enable_admin_chat_access: boolean;