chore: Fix coverage script for typescript code (#2473)

Change the nyc configuration to utilize source-maps in tandem with
typescript settings to get code coverage on our src.

Author: nbbeeken

.mocharc.json

@@ -1,8 +1,8 @@
 {
   "extension": ["js"],
-  "require": "ts-node/register",
+  "require": ["ts-node/register", "source-map-support/register"],
   "file": "test/tools/runner",
   "ui": "test/tools/runner/metadata_ui.js",
   "recursive": true,
   "timeout": 60000
-}
+}

.nycrc.json

@@ -0,0 +1,5 @@
+{
+    "extends": "@istanbuljs/nyc-config-typescript",
+    "include": ["src/**/*.ts"],
+    "reporter": ["lcovonly", "text-summary"]
+}