docs(README): fix code block type (denoland#7845)

README.md

@@ -64,7 +64,7 @@ deno run https://deno.land/std/examples/welcome.ts
 
 Or a more complex one:
 
-```sh
+```ts
 import { serve } from "https://deno.land/std@$STD_VERSION/http/server.ts";
 const s = serve({ port: 8000 });
 console.log("http:https://localhost:8000/");