Search for users to start a new DM.
Hooks up the create room UI to the matrix client to get
search results. Searches are debounced for 500ms and
only executed when 3 or more characters are entered.
Wrap the result state so we can distinguish between
"no results because we haven't searched yet" and
"no results because the API returned nothing", and
add a "No results found" message in the UI for the
latter case.
Closes#95
99f571b4eb