[web] Keyboard support for typeahead [8/13] - Add positive modulo function

Summary:
Added function for calculating positive value of number mod base.
It will be needed in further diffs to wrap value back to 0 when it overflows max value (and vice verse)

Test Plan:
Typeahead without keyboard support works.
Final tests performed in last diffs.

Reviewers: inka, kamil, ginsu, tomek

Reviewed By: inka, tomek

Subscribers: ashoat, atul, tomek, ginsu, kamil, inka

Differential Revision: https://phab.comm.dev/D6048