add code coverage (#852)

Add Cypress code coverage using Istanbul nyc

![image](https://github.com/maputnik/editor/assets/60476837/e7c364b7-7b54-4bf1-85aa-ee6fb19cc40c)

---------

Co-authored-by: shelly_goldblit <shelly_goldblit@dell.com>
Co-authored-by: Harel M <harel.mazor@gmail.com>

package.json

@@ -2,6 +2,7 @@
   "name": "maputnik",
   "version": "2.0.0-pre.2",
   "description": "A MapLibre GL visual style editor",
+  "type": "module",
   "main": "''",
   "scripts": {
     "start": "vite",
@@ -85,6 +86,8 @@
     }
   },
   "devDependencies": {
+    "@cypress/code-coverage": "^3.12.15",
+    "@istanbuljs/nyc-config-typescript": "^1.0.2",
     "@rollup/plugin-replace": "^5.0.5",
     "@shellygo/cypress-test-utils": "^2.0.9",
     "@storybook/addon-a11y": "^7.6.5",
@@ -137,6 +140,7 @@
     "stylelint-scss": "^4.2.0",
     "typescript": "^5.3.3",
     "uuid": "^8.3.2",
-    "vite": "^5.0.0"
+    "vite": "^5.0.0",
+    "vite-plugin-istanbul": "^5.0.0"
   }
 }