Rename srml to interfaces (#1198)

* Rename srml to interfaces

* newline, package.json

packages/api-derive/src/session/info.ts

@@ -2,7 +2,7 @@
 // This software may be modified and distributed under the terms
 // of the Apache-2.0 license. See the LICENSE file for details.
 
-import { BlockNumber } from '@polkadot/types/srml/types';
+import { BlockNumber } from '@polkadot/types/interfaces';
 import { DerivedSessionInfo } from '../types';
 
 import BN from 'bn.js';