op[]: mention lists of indices and non-collections

[yecril71pl]

PR Summary

Add missing information about the behaviour of operator[] with lists of indices and with non-collections.

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[opbld33]

Docs Build status updates of commit abc4053:

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reference/7.2/Microsoft.PowerShell.Core/About/about_Operators.md	✅Succeeded	View (powershell-7.2)

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[sdwheeler]

Thanks for the submission. I have several pieces of feedback for you. See my comments below.

Also, when submitting changes to a file, the changes need to be made to all versions of the file. You have submitted two PRs for the same file (about_Operators). Please combine the changes in one PR. Include all versions of the changed file in the PR.

If you want to wait for feedback before copying the changes to the other versions, mark the PR as a Work-in-Progress [WIP] as described in the PR template. After the feedback you can make the necessary changes to all version and update the PR.

[sdwheeler]

.. is the range operator so it is better described as: "Give a range of indices...".

The example is overly complicated. It is better to just show the output. For example:

PS> '123'[2..0]

3
2
1

[sdwheeler]

If an object is not an indexed collection, accessing first element returns the object itself. Index values beyond the first element return $null.

All of those zeros can be confusing. I suggest the following

PS> (2)[0] -eq 2
True
PS> (2)[-1] -eq 2
True
PS> (2)[1] -eq $null
True
PS> (2)[0,0] -eq $null
True

Style note - all keywords and operators should be lowercase

[sdwheeler]

Closing this PR. Please add the necessary changes to #8280.