Style/#229 landing page lower grey section css

[daniel-cy-lu]

Lower grey section (including the three cubes) and footer responsive css completed.

Mock-up: https://www.figma.com/file/fXh58MfxEDh1ssgxQyPb5f/Overture_Refresh?type=design&node-id=1167-9957&mode=design&t=8yIZjhY1lHQIveER-0

[daniel-cy-lu]

@ciaranschutte @mistryrn Hi guys, usually Sam helps me review these responsive css, but she has a new assignment and @joneubank suggested that I tag you. For this ticket, I completed the lower grey section in the home/landing page of overture. I provided a link to the mock up in the description. Thank you for your help as always! :D

[ciaranschutte]

looking at this now

[daniel-cy-lu]

@joneubank Thanks Jon