Replace RocketChat with Discord

Signed-off-by: Matthew B White <whitemat@uk.ibm.com>

Author: mbwhite

README.md

@@ -5,7 +5,7 @@
 [![fabric-shim npm module](https://img.shields.io/npm/v/fabric-shim?label=fabric-shim)](https://www.npmjs.com/package/fabric-shim)
 [![fabric-shim-api npm module](https://img.shields.io/npm/v/fabric-shim?label=fabric-shim-api)](https://www.npmjs.com/package/fabric-shim-api)
 [![fabric-shim-crypto npm module](https://img.shields.io/npm/v/fabric-shim?label=fabric-shim-crypto)](https://www.npmjs.com/package/fabric-shim-crypto)
-[![Rocket.Chat](https://chat.hyperledger.org/images/join-chat.svg)](https://chat.hyperledger.org/channel/fabric-chaincode-dev)
+[![Discord](https://img.shields.io/discord/905194001349627914?label=discord)](https://discordapp.com/channels/905194001349627914/943090527920877598)
 
 This is the project to support the writing of Contracts with the node.js runtime.