Add prepublishOnly build step

Author: ben-rogerson

package.json

@@ -8,7 +8,8 @@
     "build": "tsc && vite build",
     "lint": "eslint . --ext ts,tsx --report-unused-disable-directives --max-warnings 0",
     "preview": "vite preview",
-    "test": "vitest"
+    "test": "vitest",
+    "prepublishOnly": "npm run build"
   },
   "exports": {
     ".": {