[UX Improvement] Change focus when opening picker

Heyo!

one thing that's been annoying me is that, when opening the emoji picker, I'm unable to just start to type to search for an emoji, and instead need to click into the picker search box.

It'd be much nicer if, after opening the emoji picker, the focused input changed to the search field in the picker.

This is also current behaviour in both Mastodon and Misskey