[web][keyserver] Webpack config and client logic to access opaque-ke2 WASM bindings

Summary:
This diff makes it possible to call the WASM bindings from web!

Depends on D7197

Test Plan:

1. I tested on both dev and prod
2. I made sure that in both, the Network tab of Chrome dev tools showed the WASM correctly downloaded
3. I tested with this patch and made sure there were no errors in both dev and prod

Reviewers: jon, atul, varun

Reviewed By: atul

Subscribers: tomek, jon

Differential Revision: https://phab.comm.dev/D7201