[Nix] Package blob

Summary: Example of packaging rust comm services with nix

Test Plan:

nix build .#comm-blob # for linux, or any mac

https://linear.app/comm/issue/ENG-2305

Reviewers: varun, atul, O1 Nix, bartek, ashoat

Reviewed By: varun, atul, O1 Nix, bartek, ashoat

Subscribers: bartek, ashoat, tomek

Differential Revision: https://phab.comm.dev/D5727