chore: Add a unit testing framework (#49)

Add vitest as a unit testing framework

Reviewed-on: #49

package.json

@@ -5,6 +5,7 @@
   "main": "index.js",
   "scripts": {
     "start": "node index.js",
+    "test": "vitest run --globals --coverage",
     "build": "ncc build index.js -o dist --external utf-8-validate --external bufferutil"
   },
   "dependencies": {
@@ -13,6 +14,8 @@
     "screeps-api": "^1.7.2"
   },
   "devDependencies": {
-    "@vercel/ncc": "^0.38.4"
+    "@vercel/ncc": "^0.38.4",
+    "@vitest/coverage-v8": "^4.0.16",
+    "vitest": "^4.0.16"
   }
 }