[Web] Package opaque-ke-wasm files

Summary:
Include generated wasm files, and add script to create them.

https://linear.app/comm/issue/ENG-3387

Test Plan:
Not sure about packaging this with npm, but the script can be tested:

cd web/opaque-ke-wasm/
yarn build
ls pkg/

Reviewers: ashoat, varun

Reviewed By: ashoat

Subscribers: tomek, atul

Differential Revision: https://phab.comm.dev/D7197