[landing] added hover effect to investor profile cards

Summary:
added color to profile photos and a subtle glow effect whenever the cards are hovered over. One thing to note: some photos are B&W or have very little saturation already, so the hover effect sometimes doesn't seem very apparent.

Linear Task: ENG-2105

Test Plan:
Please watch the before and after video demos to see the changes I made:

Before:

After:

Reviewers: atul, rohan

Reviewed By: atul

Subscribers: ashoat, tomek, atul, abosh

Differential Revision: https://phab.comm.dev/D5481