feat: use custom variable replacement instead of vites

Author: JonasKruckenberg

example/package.json

@@ -7,6 +7,7 @@
     "serve": "vite preview"
   },
   "dependencies": {
+    "magic-string": "^0.25.7",
     "vue": "^3.0.5"
   },
   "devDependencies": {
@@ -15,4 +16,4 @@
     "typescript": "^4.1.3",
     "vite": "^2.0.5"
   }
-}
+}