Keep history for chat message bar

[cscott]

...using https://github.com/component/history ?

This makes correcting chatbot commands easier.

[Torgen]

Should the history be shared between chat rooms, or unique to each room? Should it be unique to each browser tab, shared between tabs on the same computer (i.e. local storage), or shared between computers (i.e. a subscription to the things you've said in the past)?