Add coverage script

Author: bregwin

package.json

@@ -14,6 +14,7 @@
   "main": "./src/main.js",
   "scripts": {
     "test": "node --experimental-vm-modules node_modules/jest/bin/jest.js",
+    "test:coverage": "node --experimental-vm-modules node_modules/jest/bin/jest.js --coverage",
     "format": "prettier --write \"**/*.{js,ts,html,css,md,json}\"",
     "lint": "eslint . ",
     "lint:fix": "eslint . --fix "