[1/2] [landing] get functional CTA button in hero content in mobile view

Summary:
add click cta button and functionality, styling will come in the next diff

Test Plan: click the cta in mobile review hero component. Make sure it doesn't show in desktop view

Reviewers: atul, ashoat

Reviewed By: atul, ashoat

Subscribers: ashoat, palys-swm, Adrian, karol-bisztyga, boristopalov

Differential Revision: https://phabricator.ashoat.com/D2636