Add test coverage to TS Client tests (#2409)

.gitignore

@@ -54,4 +54,5 @@ ipch/
 *.exe
 *.aps
 *.opendb
-*.db
+*.db
+coverage/

clients/ts/package.json

@@ -5,7 +5,8 @@
   "main": "index.js",
   "scripts": {
     "build": "cd ./signalr && npm run build && cd ../signalr-protocol-msgpack && npm run build",
-    "test": "jest"
+    "test": "jest",
+    "coverage": "jest --coverage"
   },
   "author": "Microsoft",
   "license": "Apache-2.0",