feat: Document new debug functions

[paulbutcher]

Fixes #4698

[magnus-madsen]

Minor comments:

• I expected myAdd to take two numbers, but okay.
• "Result in error" perhaps we should clarify this is a compile time error, not a runtime error.
• I think in the section " Source location and expression" it would be nice to show the output of the three forms.

But I will merge now.

[magnus-madsen]

FYI: The cron script that deploys runs automatically every hour.