Upgrade the "What is Monarch?" section of the landing page

[sagehrke]

On the landing page there is a section called "What is Monarch?" that currently has four icons with descriptions of how to use the Monarch Initiative. https://monarchinitiative.org/#what-is-monarch

This section is clunky and we'd like to update it to be more user friendly. The current idea is to make a carousel of how each user (informaticians, patients, clinicians, researchers) could use the Monarch Initiative tools/ontologies/etc.