[landing] added social links to investor cards

Summary:
added social links to investor cards. For the design, I went with atul's idea to have the social icons justified to the left. I also went with the white hover tint because after a second thought, I felt the colors seemed a bit too "loud" especially since everything is black/white. This diff also adds Ranjan Pradeep to the investor directory.

Linear Task: ENG-1953
Figma: Investor Page

Depends on D5390

Test Plan:
Please watch the demo video to see how the investor page looks/performs with the new social icons:

After feedback the investor profile cards now have a globe icon instead of the external link icon; demo runs exactly the same minus that one change

Investor Profile cards with globe icon:

Demo:

Reviewers: atul, rohan, ashoat

Reviewed By: atul, rohan, ashoat

Subscribers: ashoat, tomek, atul, abosh

Differential Revision: https://phab.comm.dev/D5449