compose: Add side margin to fa-exchange icon.
compose: Add side margin to fa-exchange icon.

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