Improve the keyboard navigation options in the paged display provided by `ShowCommandHelp` (F1)

[mklement0]

Prerequisites

• Write a descriptive title.

Description of the new feature/enhancement

Pressing F1 (bound to function ShowCommandHelp) helpfully provides a paged display of the help topic for the command to the left of the cursor.

However, the keyboard navigation provided is currently limited to line-by-line scrolling (up- and down-arrow keys).

It would be helpful to also support keys for the following navigation keys (possibly also via alternate keys if required for cross-platform compatibility):

• PageUp/Down (scroll a page up / down)
• Home/End (scroll to the top / bottom)

Additional commands could be implemented, which would make F1 a "one-stop shop" for all help needs, so that user won't need to use Get-Help explicitly (though, of course, are free to).

• o to open the online help (equivalent of Get-Help -Online)
• x to jump to the EXAMPLES section (analog of Get-Help -Examples
• f to search within the topic and jump to matches

[Andrew74L]

Additional commands could be implemented, which would make F1 a "one-stop shop" for all help needs, so that user won't need to use Get-Help explicitly (though, of course, are free to).

If the command to the left of the cursor is a part of a language construct, like for, foreach, do, and while, F1 has no effect.

[mklement0]

@Andrew74L, as discussed in PowerShell/PowerShell#19076 (comment), please create a new issue that suggests that F1 also recognize language keywords and conceptual help topics.

[mklement0]

See:

• ShowCommandHelp (F1) doesn't work for about_* topics relating to language keywords, specifically, if the "about_" prefix isn't used. #3570

[StevenBucher98]

I think this would make the most sense to put in the https://github.com/PowerShell/pager repo. cc @adityapatwardhan