Common HTTP server usage guide (#8732)

Co-authored-by: Georgijs <48869301+gvilums@users.noreply.github.com>

docs/guides/http/server.md

@@ -0,0 +1,46 @@
+---
+name: Common HTTP server usage
+---
+
+This starts an HTTP server listening on port `3000`. It demonstates basic routing with a number of common responses and also handles POST data from standard forms or as JSON.
+
+See [`Bun.serve`](/docs/api/http) for details.
+
+```ts
+const server = Bun.serve({
+  async fetch (req) {
+    const path = new URL(req.url).pathname;
+
+    // respond with text/html
+    if (path === "/") return new Response("Welcome to Bun!");
+
+    // redirect
+    if (path === "/abc") return Response.redirect("/source", 301);
+
+    // send back a file (in this case, *this* file)
+    if (path === "/source") return new Response(Bun.file(import.meta.file));
+
+    // respond with JSON
+    if (path === "/api") return Response.json({ some: "buns", for: "you" });
+
+    // receive JSON data to a POST request
+    if (req.method === "POST" && path === "/api/post") {
+      const data = await req.json();
+      console.log("Received JSON:", data);
+      return Response.json({ success: true, data });
+    }
+
+    // receive POST data from a form
+    if (req.method === "POST" && path === "/form") {
+      const data = await req.formData();
+      console.log(data.get("someField"));
+      return new Response("Success");
+    }
+
+    // 404s
+    return new Response("Page not found", { status: 404 });
+  }
+})
+
+console.log(`Listening on ${server.url}`);
+```