[lib] Add function to ed25519 verify message to OlmAPI

Summary:
Exposed function from D11905 via OlmAPI and made it return boolean instead of try-catch based approach.

Depends on D11905

Test Plan:

const { olmAPI } = getConfig();
const pubKey = await getContentSigningKey();
const signature = await olmAPI.signMessage('hello');
const isValid = await olmAPI.verifyMessage('hello', signature, pubKey);
console.log(isValid ? 'valid' : 'invalid');

on both native and web

Reviewers: kamil, marcin

Reviewed By: kamil

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D11907