docs: Document Transifex steps for new major releases.
docs: Document Transifex steps for new major releases.

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