RetryError: ERR_HTTP2_GOAWAY_SESSION

Hi there! Coming from node-fetch for the h2 support. Everything looked great when I first made the swap, but I just noticed that if I leave the app open for a while, subsequent requests will all end up getting this error:

```
err: {
"type": "RetryError",
"message": "ERR_HTTP2_GOAWAY_SESSION",
"stack":
Error: ERR_HTTP2_GOAWAY_SESSION
at doFetch (C:\Users\Lewis\Develop\reflame\code\agent\node_modules\fetch-h2\dist\lib\fetch-http2.js:56:23)
}
```

The only way to recover I've found was to restart the app, which is obviously not great. 😅

I followed the error trace to this line: https://github.com/grantila/fetch-h2/blob/502c7daf37c4e40eba23da392b8cc708ee84b20d/lib/fetch-http2.ts#L137

The comment above says `// Retry with new session`, but the code itself just throws. Maybe the retry behavior hasn't been implemented yet?