`--title` in `new-tab` sets the pane's title, not the tab's

https://docs.microsoft.com/en-us/windows/terminal/command-line-arguments?tabs=windows#tab-title

we should add an example like 

```powershell
wt nt --title Test -d C:/Users `; sp -d C:/Windows
```

and clarify that `--title` sets the title for the _pane_, not the tab. 

See https://github.com/microsoft/terminal/issues/12459