refactor: Rename Deno main file to index.ts and update import

deno/main.ts

@@ -1,10 +0,0 @@
-export function add(a: number, b: number): number {
-  return a + b;
-}
-
-// Learn more at https://docs.deno.com/runtime/manual/examples/module_metadata#concepts
-if (import.meta.main) {
-  console.log("Add 2 + 3 =", add(2, 3));
-}
-
-Deno.serve({ hostname: "0.0.0.0", port: 8000 }, () => new Response("Hello, world!"));