feat: improve emoji autocomplete

[SychO9]

Changes proposed in this pull request:

• The current emoji autocomplete opens up by default by listing the first items on the emoji map from the cdn.
• This PR make it so that the common smileys are listed by default.
• This PR also improves the emoji autocomplete UX.

Before

After

Necessity

• [x] Has the problem that is being solved here been clearly explained?
• [x] If applicable, have various options for solving this problem been considered?
• [x] For core PRs, does this need to be in core, or could it be in an extension?
• [x] Are we willing to maintain this for years / potentially forever?

Confirmed

• [x] Frontend changes: tested on a local Flarum installation.
• [x] Backend changes: tests are green (run composer test).
• [x] Core developer confirmed locally this works as intended.
• [x] Tests have been added, or are not appropriate here.

[dsevillamartin]

Could it be made so the name of the currently selected icon shows up in either placeholder or a tooltip? That way the name can be learned, as otherwise one would need to guess or keep selecting from the autocomplete every time. I see the alt attribute on the image, not sure if anything else would be better or helpful. Just a thought.

Otherwise, I like the changes! :+1:

[SychO9]

@dsevillamartin it also has tooltips if that's you mean

[dsevillamartin]

@SychO9 Oh, I did not see the code. Forgot how tooltips worked nowadays for a sec. :+1:

[imorland]

@SychO9 if you can take care of the conflict, this is ready to merge :)