Add about_PowerShell_Config (#3238)

* Add first json entries

* Add ExperimentalFeatures heading

* Add experimental feature documentation

* Change heading usage

* Add headers for remaining configuration topics

* Add logging configuration information

* Comment out GPO settings

* Add examples

* Add special document folder hack

* Editorial changes

@rjmholt Please review these changes.

* Update reference/6/Microsoft.PowerShell.Core/About/about_PowerShell_Config.md

Co-Authored-By: rjmholt <[email protected]>

* Fix up PSModulePath documentation

* Add execution policy note

* Formatting per About_ topic rules

* Correct examples, add warning about module scopes

Author: rjmholt