help: Activate sidebar scrollbar when hamburger is clicked.
help: Activate sidebar scrollbar when hamburger is clicked.

On mobile, when you go to our /help pages, you cannot scroll the
sidebar content. As for testing, the bug can be reproduced by
using a mobile display in Chrome inspector. One caveat of this
bug is that if you go to /help with a mobile display toggled,
the scrollbar won't work. However, if you switch between
different mobile displays, it starts working.

This commit adds some JS that sets the right CSS properties
when the hamburger is clicked.

andersk/zulip,rht/zulip,hackerkid/zulip,kou/zulip,kou/zulip,zulip/zulip,eeshangarg/zulip,rht/zulip,zulip/zulip,hackerkid/zulip,andersk/zulip,kou/zulip,eeshangarg/zulip,andersk/zulip,hackerkid/zulip,hackerkid/zulip,zulip/zulip,eeshangarg/zulip,zulip/zulip,zulip/zulip,rht/zulip,eeshangarg/zulip,andersk/zulip,hackerkid/zulip,hackerkid/zulip,zulip/zulip,andersk/zulip,hackerkid/zulip,kou/zulip,kou/zulip,andersk/zulip,andersk/zulip,zulip/zulip,eeshangarg/zulip,rht/zulip,kou/zulip,eeshangarg/zulip,rht/zulip,rht/zulip,rht/zulip,eeshangarg/zulip,kou/zulip