Update README.md

Add about force_readonly

README.md

@@ -137,7 +137,7 @@ Usage
 
 - **force_readonly** as *boolean*, optional, default *false*
 
-  This option can disallow any write operations on foreign server user data througth SQLite file readonly access mode. This option driven only by foreign server owner role can not be overwritten by any `updatable` option value. This is a strong restiction by PostgreSQL foreign server owner user not to modify data in any foreign server tables. Also see [Connection to SQLite database file and access control](#connection-to-sqlite-database-file-and-access-control).
+  This option is useful if you need grant user permission to create a foreign tables on the foreign server and revoke user permission to modify any table data on this foreign server. This option with `true` value can disallow any write operations on foreign server table data througth SQLite file readonly access mode. This option driven only by foreign server owner role can not be overwritten by any `updatable` option value. This is a strong restiction given by PostgreSQL foreign server owner user not to modify data in any foreign server tables. Also see [Connection to SQLite database file and access control](#connection-to-sqlite-database-file-and-access-control).
 
 - **truncatable** as *boolean*, optional, default *false*