reference,learn: start moving custom interactions to learn

[l-zeuch]

This PR aims to move the Custom Interactions page--currently residing
inside docs/reference--to a new Advanced section in the learning course.

The short-term goal is to split the incredibly detailed page (thanks to
the amazing work of @SoggySaussages) into smaller, more digestible
sections. I oriented these splits around the already existing sections
on the mentioned page.

The long-term goal is to make space under the (debatably) filled
Reference in the main docs section, and also spark inspiration for more
advanced topics in the learning course.

Signed-off-by: Luca Zeuch [email protected]

Terms

• I have read and understood this project's Contributing Guidelines

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I am further inviting @SoggySaussages to carefully examine my changes
with the highest scrutiny, as I am not sure if I have done the original
work justice. I am also open to any suggestions for improvement.

[l-zeuch]

This first commit serves to outline my intentions with splitting up the
page.

The general idea in "Creating Interactive Elements" is to first introduce
the elements one can create in custom commands, then explain how to make
them useful--therefore I chose to elide mentions of custom_id, but
still kept those in when defining the elements, such that we can more
easily back-reference them when it comes to writing this section.

Perhaps instead of splitting "Parsing an Interaction" into a new page,
as the current headers would suggest it (going by my current logic), we
can merge it with the current WIP page? Though, I'm unsure how to
appropriately name it, then. Suggestions welcome.

[l-zeuch]

Unless I missed anything, the move should now be complete--I hope I
split the original page up reasonably well into the proposed
sub-chapters.

@SoggySaussages - would you mind giving this a review, just to make sure
it's all still there?

[l-zeuch]

As an afterthought, we should also consider shortening the reference
page to the bare minimum; I don't think outright removing it is a good
idea, especially with all the linking to it on the support server. I
also haven't checked any crosslinks in the docs themselves, yet, as well
as indicating that this guide has been moved.

[savage4618]

am I doing this right?