[new lib]coro_http_server

[qicosmos]

Why

add new lib: coro_http_server

What is changing

Example

  coro_http::coro_http_server server(1, 9001);
  server.set_http_handler<coro_http::GET, coro_http::POST>(
      "/", [](coro_http_request &req, coro_http_response &resp) {
        // response in io thread.
        resp.set_status_and_content(coro_http::status_type::ok, "hello world");
      });

  server.set_http_handler<coro_http::GET, coro_http::POST>(
      "/coro",
      [](coro_http_request &req,
         coro_http_response &resp) -> async_simple::coro::Lazy<void> {
        co_await coro_io::post([&]() {
          // coroutine in other thread.
          resp.set_status_and_content(coro_http::status_type::ok,
                                      "hello world in coro");
        });
      });

  server.sync_start();