Add online help support to keywords

[BernieWhite]

When editing .Rule.ps1 files in Visual Studio Code, keywords are imported into session to allow command completion to provide usage information.

Additionally VS Code can read help information and link out to online help with Get Help for Command. Quickly getting access to online help will improve the authoring experience for defining rules.

For this to work for PSRule keywords, comment-based help needs to provide a online link.

For example:

<#
.LINK
https://berniewhite.github.io/PSRule/keywords/PSRule/en-US/about_PSRule_Keywords.html#rule
#>