Add powershell 7 support to hasura completion

Hasura completion currently supports bash and zsh.

Tab completion is now possible in powershell, with `Set-PSReadlineKeyHandler -Key Tab -Function MenuComplete`

There is also the [Register-ArgumentCompleter](https://docs.microsoft.com/en-us/powershell/module/microsoft.powershell.core/register-argumentcompleter?view=powershell-7.1) cmdlet which could be used to implement this.

Hasura's completion should include this shell.

Start by locating Hasura's existing bash and zsh completion entry points and compare how they expose command arguments. Review PowerShell's Register-ArgumentCompleter and Set-PSReadlineKeyHandler documentation before choosing an integration path. Done means Hasura completion is available in PowerShell 7 alongside the existing shell support.

Written by the indexing model from the issue text.