Update serve documentation in the guide

[joshrotenberg]

The guide's serve.md contains out of date command line option docs. This PR brings it inline with the current state of the command.

Fixes #1524.

[ehuss]

Thanks, this looks good to me! I notice that this is in Draft state, are you intending to do more changes?

[joshrotenberg]

Thanks, this looks good to me! I notice that this is in Draft state, are you intending to do more changes?

I'm trying to decide if adding headings for --hostname and --port makes sense in the same way we have them for --open, etc. i.e.

#### --hostname
....

But I think the ### Server options section covers them. I'll mark it as ready, if you want those added I'm happy to do it.

[ehuss]

I think it's fine, thanks for the help!