Add documentation about giving hints to specific instruction steps

[fapdash]

Apparently it's possible to give hints to a specific step in the instructions.md: https://github.com/exercism/common-lisp/blob/149c61afdf0025f63e5a5dc1157e1b7882df65ff/exercises/concept/pizza-pi/.docs/hints.md?plain=1#L23-L27

Which shows up in the online editor like this:

I think that's really cool but I don't see this documented: https://github.com/exercism/docs/blob/792656920b468ed0c04f140731d3c64f7bf67573/building/tracks/practice-exercises.md?plain=1#L213-L239

Edit: I just realized that the example I gave is for a learning exercise, not a practice exercise, but since all exercises are moving to that format I assume that this will be possible for practice exercises following this format as well?

[fapdash]

Will there even be a difference between Concept Exercises and Practice Exercises or can the two documentation pages be merged?

Edit: Answered my own question, no they can't be merged, eg. concept exercises don't have a difficulty.

[fapdash]

Nevermind, practice exercises don't have instruction steps. Closing.