Update WT help to be in sync with docs.microsoft.com

[elsaco]

Windows Terminal version (or Windows build number)

10.0.19043.0 1.10.2383.0

Other Software

This issue was inspired by #11206

Steps to reproduce

• run "wt -h" to display help

Expected Behavior

• help to be in sync with https://docs.microsoft.com/en-us/windows/terminal/

Actual Behavior

Sample help output:

There's a lot more help online.

[DHowett]

There is a bit of confusion here. The -p argument is an argument to the new-tab subcommand. To see all subcommand help, use wt new-tab --help (repeat with split-pane, etc.)