feat: quick react via message editor

[mini-bomba]

Description

typing +: in the message editor will bring up the emoticon autocomplete prompt, where choosing an emoticon will clear the editor and react with that emoticon under the latest message

reactions.webm

this pr also splits the autocomplete prefixes in two: ones that can be used anywhere in the message, and those that only work at the beginning

also i set a default type param on one of the autocomplete query functions because who wants to keep typing out that type everywhere all the time

also there was some minor code deduplication and a fix to the autocomplete query system

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
  • as much as i can do myself - i'm very much new to writing matrix clients, i might've done something terribly stupid
• I have commented my code, particularly in hard-to-understand areas
  • do self-descriptive variable names and one new comment count?
• I have made corresponding changes to the documentation
• My changes generate no new warnings

[7w1]

super cool!