[lib] add localID field to reaction message type

Summary:
add localID field to reaction message type. We are going to need this to create local reaction messages which we will display optimistically

Linear Task: ENG-2519

Test Plan: flow and will be testing more in subsequent diffs

Reviewers: atul, tomek, ashoat

Reviewed By: tomek, ashoat

Subscribers: ashoat, tomek, atul

Differential Revision: https://phab.comm.dev/D6117