[web] Calendar scrolling
Summary:
ENG-1678
This diff adds a scrollbar to the calendar if it's too big vertically.
Test Plan: Test if calendar can be scrolled. Check if there is no scrollbar when it's not needed (the screen is high enough).
Reviewers: tomek, atul, abosh, ginsu
Reviewed By: tomek, ginsu
Subscribers: ashoat
Differential Revision: https://phab.comm.dev/D5472