Add block support for the WordPress Core Editor.

[georgestephanis]

Trac Ticket: https://bbpress.trac.wordpress.org/ticket/3403

[georgestephanis]

Vizrec for what I've got so far on the two:

I'd like to get a better react component available for a nested dropdown forum picker, and I'm probably going to need a better api-driven topic search (as preloading all topics isn't tenable in the same way that preloading all forum topics is)

[georgestephanis]

[georgestephanis]

I fixed the spacing between the icon and the text for the placeholder block, and added several more blocks as well.

[georgestephanis]

Added in stub textinput pickers for the remaining data types -- topics, replies, topic tags, and views. These could all be improved.

I'd love to tweak them to pull data in via the Backbone WP API Client that ships in the core, but that's very much not my area of expertise especially working with custom post types and taxonomies and such. If possible, it would also be worth retooling the Forum picker to run off that, tbh.

cc: @adamsilverstein maybe if you can give a hot take or any input here? (I think I'd heard that the backbone client is more your back yard)

[adamsilverstein]

Hey @georgestephanis thanks for the ping.

Given this is being built for the block editor, I think you have all the API's you need to get the data you want without using the Backbone client. I think we could build a data store that would fetch the data from the API.

For the select itself, a native element works well when you have a small number of items (see WordPress/gutenberg#26077), for longer lists, I suggest using the (new) accessible autocomplete/search selector ComboboxControl component. You can see sample uses of it internally in Gutenberg in the author and page parent selectors.

[adamsilverstein]

@georgestephanis I took a pass at adding the selector + data for the Forum picker in georgestephanis#1. The styling could use some work, some improvements are being worked on upstream - see https://github.com/WordPress/gutenberg/search?q=ComboboxControl+is%3Aissue&state=open&type=Issues &

I started at the most complicated one (because it is hierarchical). I'll work on something simpler next!

[georgestephanis]

Note to self: add script dependencies for wp.data wp.element and lodash (I believe they're all on the block editor page anyways, but may as well clarify them as dependencies for load order and stuff)

[dd32]

Branch restored. PR re-opened. This was accidental.
This PR doesn't need to be rebased to trunk, that'll be done by the committer.