[web] Moved typeahead utils to web/chat

Summary:
Short diff. Moved utils file from lib to web, as it will contain web specific utils.
We might consider keeping common utilites for typeahead in lib, but it can be worked out when
working on native feature.

Test Plan: Functions still visible after changing file locations.

Reviewers: tomek, kamil, atul

Reviewed By: tomek

Subscribers: ashoat, atul, kamil, tomek

Differential Revision: https://phab.comm.dev/D5717