feat: Enable endpoint pooling configuration

[ghost]

Take it for a spin in your own project!

1. Clone the repo and checkout this branch
2. Run cargo build in the root directory
3. Run yarn build in the root directory (generates a production version of the sdk as a node package)
4. Copy the newly created *.node file into your own node project
5. Start a server on whatever two ports you'd like (I use `python -m http.server 3000 && python -m http.server 8000)
6. Open the url of your ngrok reserved domain in the browser
7. Observe that both ports (3000 and 8000) show the http requests!

index.js

// Require ngrok javascript sdk
const ngrok = require("./ngrok.darwin-arm64.node");
// import ngrok from '@ngrok/ngrok' // if inside a module

(async function () {
  // Establish connectivity
  const builder = new ngrok.SessionBuilder().authtokenFromEnv();
  builder.connect().then((session) => {
    session
      .httpEndpoint()
      .domain("/* your domain */")
      .poolingEnabled(true)
      .listen()
      .then((listener) => {
        console.log(`Ingress established at: ${listener.url()}`);
        listener.forward("http://localhost:3000");
      });
  });
  builder.connect().then((session) => {
    session
      .httpEndpoint()
      .domain("/* your domain */")
      .poolingEnabled(true)
      .listen()
      .then((listener) => {
        console.log(`Ingress established at: ${listener.url()}`);
        listener.forward("http://localhost:8000");
      });
  });
})();

process.stdin.resume();

[bmpngrok]

LGTM!