Replace sample code with embedded `MarkDownSnippets` to guarantee code is current and code works

[goblinfactory]

similar to #65 I think.
Now that I stumbled across the excellent MarkDownSnippets I can update the sample code. Woot!
https://github.com/SimonCropp/MarkdownSnippets

I won't list all the examples here that need to be updated, I'll simply do an audit of sample code that should be changed as part of this ticket, then make the changes, and submit a PR.

Included as part of this ticket will be ensuring that the code that the docs are referring to still in fact exists, and if not the docs need to be updated to reflect the latest changes, if needed.

[rofr]

Go for it!