add namespace wiki article with scripted update

[FH-Inway]

Adds a Namespaces.md wiki article, based on Abbreviations. Command lists in the article are updated by new logic in build/update-docs.ps1.

Preview of wiki article on my fork: https://github.com/FH-Inway/d365bap.tools/wiki/Namespaces

Documentation automation and improvements:

• Added a new PowerShell function Update-NamespacesArticle to build/update-docs.ps1 that automatically updates the wiki/Namespaces.md file with tables of commands and their descriptions for each namespace, using comment-based help from the module.
• The markdown help generation in the build script is now conditional on the presence of platyPS (the New-MarkdownHelp command); if not installed, a warning is shown.
• Created a new, well-structured wiki/Namespaces.md file that explains the concept of namespaces/abbreviations, provides links and usage examples, and includes auto-generated tables of all commands for each namespace (Bap, Ppac, Fscm, Ppe, Ude, Unified, Graph), with descriptions pulled from their help synopsis.
• The documentation now clearly states that the tables are auto-generated by the build process, ensuring they are always up to date.

These changes make it much easier for users to discover and understand the available commands in the module, and ensure that documentation stays current with the codebase.

[FH-Inway]

@Splaxi After seeing the latest prs with the Ppe commands and wondering what that namespace is about, I added this article based on your LinkedIn article. Still getting used to all those namespaces, but I now realized the difference between Ude and Unified 😄