docs: Include simplified link titles in main index

Include simplified link titles in the main page's documentation index to
enhance website's readability and UX. Update the text that directs users to
various documents without changing the actual titles chosen by the authors.

Signed-off-by: Carlos Bilbao <carlos.bilbao@amd.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/20240109155643.3489369-3-carlos.bilbao@amd.com