Better media conn handling

src/WAConnection/0.Base.ts

@@ -20,6 +20,7 @@ import {
     WAQuery,
     ReconnectMode,
     WAConnectOptions,
+    MediaConnInfo,
 } from './Constants'
 import { EventEmitter } from 'events'
 import KeyedDB from '@adiwajshing/keyed-db'
@@ -74,6 +75,8 @@ export class WAConnection extends EventEmitter {
     protected lastDisconnectTime: Date = null
     protected lastDisconnectReason: DisconnectReason 
 
+    protected mediaConn: MediaConnInfo
+
     constructor () {
         super ()
         this.registerCallback (['Cmd', 'type:disconnect'], json => (