help_docs: Add 'About Zulip' to relative help links.
help_docs: Add 'About Zulip' to relative help links.

Adds the 'About Zulip' gear menu option to the available
relative link patterns used in help center documentation.

rht/zulip,rht/zulip,rht/zulip,andersk/zulip,rht/zulip,andersk/zulip,andersk/zulip,andersk/zulip,rht/zulip,andersk/zulip,rht/zulip,zulip/zulip,zulip/zulip,zulip/zulip,andersk/zulip,zulip/zulip,zulip/zulip,zulip/zulip,zulip/zulip,andersk/zulip,rht/zulip