add tsc watch script

Author: craigmichaelmartin

package.json

@@ -15,7 +15,8 @@
     "format": "prettier --write  \"**/*.{ts,js,json,md}\" \"!coverage/**/*\"",
     "lint": "eslint .",
     "pub": "npm run test && npm run build && np",
-    "build": "rm -rf dist && mkdir -p dist && cp -r test-utils dist/test-utils && tsc"
+    "build": "rm -rf dist && mkdir -p dist && cp -r test-utils dist/test-utils && tsc",
+    "build:watch": "rm -rf dist && mkdir -p dist && cp -r test-utils dist/test-utils && tsc --watch"
   },
   "dependencies": {
     "@babel/core": "^7.17.9",