types/Sharedb - add an optional agent parameter to the client connection (#41955)

* add an optional agent to the client sharedb connection

* remove myself as a contributor, set agent to be agent or null

* add docs

types/sharedb/lib/client.d.ts

@@ -1,9 +1,15 @@
 /// <reference path="sharedb.d.ts" />
 import * as WS from 'ws';
 import * as ShareDB from './sharedb';
+import Agent = require('./agent');
 
 export class Connection {
     constructor(ws: WebSocket | WS);
+
+    // This direct reference from connection to agent is not used internal to
+    // ShareDB, but it is handy for server-side only user code that may cache
+    // state on the agent and read it in middleware
+    agent: Agent | null;
     get(collectionName: string, documentID: string): Doc;
     createFetchQuery(collectionName: string, query: any, options: {results?: Query[]}, callback: (err: Error, results: any[]) => void): Query;
     createSubscribeQuery(collectionName: string, query: any, options: {results?: Query[]}, callback: (err: Error, results: any[]) => void): Query;