silence sveltekit tsconfig warning

Your tsconfig.json should extend the configuration generated by SvelteKit:
{
  "extends": "./.svelte-kit/tsconfig.json"
}

tsconfig.json

@@ -1,5 +1,5 @@
-// https://github.com/sveltejs/language-tools/blob/master/docs/preprocessors/typescript.md
 {
+  "extends": "./.svelte-kit/tsconfig.json",
   "compilerOptions": {
     "strict": true,
     "module": "esnext",