[web] Introduce getRelatedMessages to shared worker
Summary:
This diff introduces the code on web to interface with our new getRelatedMessages API exposed via WASM.
Depends on D12737
Test Plan:
- In combination with later diffs, I tested a patch on both native and web that hit getRelatedMessages with a specific message ID and confirmed that it returned the message
- I tested a message ID that did not exist and confirmed I got undefined back
Reviewers: kamil, tomek, marcin
Reviewed By: marcin
Differential Revision: https://phab.comm.dev/D12738