Support for advanced autocomplete features like brew packages

[vaaski]

Is your feature request related to a problem? Please describe. Moving to inshellisense from Fig, I've been missing advanced autocomplete features like when installing or upgrading brew packages.

Fig suggesting from a list of available packages.

It seems like the functionality is already included in the autocomplete specs, but I don't see any suggestions with inshellisense.

https://github.com/withfig/autocomplete/blob/d73d606281aa7a6e812654b045ba7d15fa4f4bb2/src/brew.ts#L1116