Add sendSignal() helper

[MasterKale]

This PR adds a new sendSignal() method to @simplewebauthn/browser to simplify use of the WebAuthn Signal APIs. The WebAuthn Signal APIs are fire-and-forget methods that help Relying Parties (i.e. websites using SimpleWebAuthn for passkeys) try to communicate passkey state changes through the browser and back to an authenticator that may have a passkey for the website. No signal is guaranteed to make it to such an authenticator; WebAuthn Signal API calls (including those made using this new sendSignal() method) are "best effort."

Types for the three possible shapes of options that can be passed into this method are also exported. Types include descriptions of each signal and offer advice on when to use them (https://simplewebauthn.dev will get updated shortly after release with new docs for this method as well):

import {
  sendSignal,
  type SendSignalAllAcceptedCredentialsOpts,
  type SendSignalCurrentUserDetailsOpts,
  type SendSignalUnknownCredentialOpts,
} from '@simplewebauthn/browser';

These same type's are also exported from @simplewebauthn/server to offer RPs typing that can be used when crafting server-side APIs to generate and return these options to pass into sendSignal() in the browser:

import type {
  SendSignalAllAcceptedCredentialsOpts,
  SendSignalCurrentUserDetailsOpts,
  SendSignalUnknownCredentialOpts,
} from '@simplewebauthn/server';

Examples

PublicKeyCredential.signalUnknownCredential()

import {
  sendSignal,
  type SendSignalUnknownCredentialOpts,
} from '@simplewebauthn/browser';

const opts: SendSignalUnknownCredentialOpts = {
  signalName: 'unknownCredential',
  rpID: 'example.com',
  credentialID: 'aPH2yv3TIBVZbj2wJ30Kmw',
};
await sendSignal(opts);

PublicKeyCredential.signalAllAcceptedCredentials()

import {
  sendSignal,
  type SendSignalAllAcceptedCredentialsOpts,
} from '@simplewebauthn/browser';

const opts: SendSignalAllAcceptedCredentialsOpts = {
  signalName: 'allAcceptedCredentials',
  rpID: 'example.com',
  userID: 'Lrk2ki-arSSFcm6PPlMKEQ',
  allAcceptedCredentialIDs: [
    'd77Hxqvltn66l7hegq_E3Q',
    'nz_ajzNrMq3KfPrkOt3lHQ',
  ],
};
await sendSignal(opts);

PublicKeyCredential.signalCurrentUserDetails()

import {
  sendSignal,
  type SendSignalCurrentUserDetailsOpts,
} from '@simplewebauthn/browser';

const opts: SendSignalCurrentUserDetailsOpts = {
  signalName: 'currentUserDetails',
  rpID: 'example.com',
  userID: 'Lrk2ki-arSSFcm6PPlMKEQ',
  userName: 'newUsername@example.com',
  userDisplayName: 'NewUsername (Prod)',
};
await sendSignal(opts);

Fixes #718.