Create basic web server framework

- uses HOSTNAME env var for root domain, falling back to locahost
- uses PORT env var for port, falling back to 8000 (as non privileged)
- extracts subdomain from url and WILL match it, but not currently
- Returns "404 could not resolve domain" if not matched

deno.json

···
+{
+  "tasks": {
+    "dev": "deno run --watch --allow-net --allow-env=HOSTNAME,PORT main.ts"
+  },
+  "imports": {}
+}

main.ts

···
+const ROOT_DOMAIN = Deno.env.get("HOSTNAME") || "localhost";
+const SUBDOMAIN_REGEX = new RegExp(`.+(?=\\.${ROOT_DOMAIN}$)`, "gm");
+
+Deno.serve(
+  { port: parseInt("" + Deno.env.get("PORT")) || 8000, hostname: ROOT_DOMAIN },
+  (req) => {
+    const reqUrl = new URL(req.url);
+    const subdomain = reqUrl.hostname.match(SUBDOMAIN_REGEX)?.at(0);
+
+    return new Response(
+      `Could not resolve domain "${subdomain ?? ""}${subdomain ? "." : ""}${ROOT_DOMAIN}"`,
+      {
+        status: 404,
+      }
+    );
+  }
+);