`bsb -ws` flag is undocumented

[Kingdutch]

When I run bsb -help there is info about all the available flags. However there's no documentation for -ws which is a valid flag.

It is documented in the ReasonReact hooks example as follows:

// package.json's `start` script's `bsb -ws _` means it'll pipe build events
// through a websocket connection to a default port of 9999. This is
// configurable, e.g. `-ws 5000`

That's a pretty odd place to find the documentation for the flag because someone may want to use the Websocket events outside of ReasonReact.

If the flag should not generally be used then it may still be useful to make the help command link to more extensive documentation where the flag can be documented as dangerous.