Presentations page: Move how-to-add instructions to the end of the page

Most visitors are readers looking for presentations, fewer are looking
for the description how to add new presentations. Hence these
instructions are moved to the end of the page.

Bug: Issue 13332
Signed-off-by: Edwin Kempin <ekempin@google.com>
Change-Id: Icd41f14e4170c3a076e4bb084e9bf88683411db8
1 file changed