(#1074) Add docs for Get-ChocolateyConfigValue

[vexx32]

Description Of Changes

Add/move docs for Get-ChocolateyConfigValue cmdlet as it's being rewritten

Motivation and Context

Keeping up with the changes to the cmdlets feature branch in choco repo, putting docs here too as we go

Testing

• I have previewed these changes using the Docker Container or another method before submitting this pull request.

Change Types Made

• Minor documentation fix (typos etc.).
• Major documentation change (refactoring, reformatting or adding documentation to existing page).
• New documentation page added.
• The change I have made should have a video added, and I have raised an issue for this.
  • Issue #

Change Checklist

• Requires a change to menu structure (top or left-hand side)/
• Menu structure has been updated

Related Issue

Fixes #1074

[gep13]

This needs to be updated, right?

[gep13]

Is there an alias for -ConfigKey, as this is what the previous version of -Name was.

NOTE: I haven't got to the other PR yet 😄

[gep13]

Never mind, I can see this in play in the example below.