Wrote 'Custom Editor Actions' page

[deanljohnson]

Summary

Wrote a docs page on "Custom Editor Actions"

Topics

• What is an editor action?
• EditorAction and EditorSingleAction
• Retrieving EditorActions
• Action contexts

I placed the page under the "advanced" category, but as more docs on extending the editor are written it might make more sense to move this into a new "Extending the Editor" category.

[ilexp]

Pinging the @AdamsLair/duality-docs team for a first review

[ilexp]

Solid explanation, brief and to the point 👍

[ilexp]

I placed the page under the "advanced" category, but as more docs on extending the editor are written it might make more sense to move this into a new "Extending the Editor" category.

Sounds good. Maybe go with an "Editor" top-level category later on, and spread out from there. We're using top-level categories for most things right now, but as the number of articles grows, we should adopt a hierarchical structure, as done for the two Guidelines pages Best Practices and Common Pitfalls. The generation code is already in place, just need to use the parent page variable instead of category.