[lib/native] add more icons to comm icon pack

Summary:
This diff adds the following new icons to the CommIcon pack: reply-filled, link_plus-outline, unpin-outline and pin-outline. These changes were copy and pasted from files given to me by Ted.

I also added the icons to our dropbox

Test Plan:
Tested every icon to make sure there were no regressions, and here are the screenshots for the new icons

reply-filled

link_plus-outline

unpin-outline

pin-outline

Reviewers: ashoat, atul

Reviewed By: atul

Subscribers: rohan, ashoat, tomek, atul

Differential Revision: https://phab.comm.dev/D7737