Fix broken links in 01.browser-echo readme

Fixes #1751

samples/javascript_es6/01.browser-echo/README.md

@@ -2,7 +2,7 @@
 
 Bot Framework v4 browser bot sample
 
-The example shows the use of the `botbuilder-js` SDKs for the browser using the [BotFramework-WebChat](https://github.com/Microsoft/BotFramework-WebChat) and a custom [WebChatAdapter](/src/webChatAdapter.js).
+The example shows the use of the `botbuilder-js` SDKs for the browser using the [BotFramework-WebChat](https://github.com/Microsoft/BotFramework-WebChat) and a custom [WebChatAdapter][1].
 
 ## To try this sample
 
@@ -42,7 +42,7 @@ The example shows the use of the `botbuilder-js` SDKs for the browser using the
 
 Developers can use the [BotAdapter](https://docs.microsoft.com/en-us/javascript/api/botbuilder-core/botadapter) abstract base class to implement their own custom adapters.
 Implementing a custom adapter allows users to connect bots to channels not supported by the [Bot Framework](https://docs.microsoft.com/en-us/azure/bot-service/bot-service-manage-channels?view=azure-bot-service-4.0).
-In this sample, a custom [WebChatAdapter](./src/WebChatAdapter.js) has been implemented so that the entirety of the bot is hosted in a user's browser.
+In this sample, a custom [WebChatAdapter][1] has been implemented so that the entirety of the bot is hosted in a user's browser.
 
 Hosting a bot in the browser provides these benefits:
 
@@ -55,3 +55,5 @@ Hosting a bot in the browser provides these benefits:
 - [Azure Bot Service](https://docs.microsoft.com/en-us/azure/bot-service/bot-service-overview-introduction?view=azure-bot-service-4.0)
 - [Activity processing](https://docs.microsoft.com/en-us/azure/bot-service/bot-builder-concept-activity-processing?view=azure-bot-service-4.0)
 - [Bot State and storage](https://docs.microsoft.com/en-us/azure/bot-service/bot-builder-storage-concept?view=azure-bot-service-4.0)
+
+  [1]: ./src/webChatAdapter.ts