Exposing web3.eth.Contract.setProvider() as per public documentation

packages/web3-eth-contract/types/index.d.ts

@@ -19,6 +19,7 @@
 
 import BN = require('bn.js');
 import {Common, PromiEvent, provider, hardfork, chain, BlockNumber, PastLogsOptions, LogsOptions} from 'web3-core';
+import {Accounts} from 'web3-eth-accounts';
 import {AbiItem} from 'web3-utils';
 
 // TODO: Add generic type!
@@ -29,6 +30,8 @@ export class Contract {
         options?: ContractOptions
     );
 
+    static setProvider(provider: provider, accounts?: Accounts): void;
+
     private _address: string;
     private _jsonInterface: AbiItem[];
     defaultAccount: string | null;