This was definitely added at someone's request, since I wouldn't have
put it here. But it's displayed below in the details section already and
also not displayed in the updated "wedge" in the new design.
See https://github.com/ppy/osu/discussions/17537 for discussion.
Reference design: https://www.figma.com/file/f8b2dHp9LJCMOqYP4mdrPZ/Client%2FChat?node-id=1%3A297
Adds new component `ChatTextBox`.
Exposes `BindableBool` `ShowSearch` to change text input behaviour
between normal and search behaviour.
Adds new component `ChatTextBar`.
Exposes `BindableBool` `ShowSearch` which toggles between showing current
chat channel or search icon.
Additionally binds to child `ChatTextBox` components.
Requires a cached `Bindable<Channel>` instance to be managed by a parent
component.