Add port environment

Author: ryo-ma

env-example

@@ -1,3 +1,4 @@
+PORT=8080
 GITHUB_TOKEN1=
 GITHUB_TOKEN2=
 GITHUB_API=https://api.github.com/graphql

debug.ts main.tsdebug.ts renamed to main.ts

@@ -1,4 +1,4 @@
 import { serve } from "https://deno.land/std@0.125.0/http/server.ts";
 import requestHandler from "./api/index.ts";
 
-serve(requestHandler, { port: 8080 });
+serve(requestHandler, { port: Number(Deno.env.get("PORT")) || 8080 });