Function generateCodeChallenge

generateCodeChallenge(verifier: string): Promise<string>
Derive the S256 PKCE code challenge from a code verifier.

Computes BASE64URL(SHA256(verifier)) using the Web Crypto API (SubtleCrypto), available in Node 18+ and modern browsers.
Parameters
- verifier: string
  The code verifier string (typically from generateCodeVerifier)
Returns Promise<string>
The base64url-encoded SHA-256 hash of the verifier
Example
```
import { generateCodeVerifier, generateCodeChallenge } from 'soundcloud-api-ts';

const verifier = generateCodeVerifier();
const challenge = await generateCodeChallenge(verifier);
console.log(challenge); // e.g. "dBjftJeZ4CVP-mB92K27uhbUJU1p1r_wW1gFWFOEjXk"
```
See
https://datatracker.ietf.org/doc/html/rfc7636#section-4.2
- Defined in src/auth/pkce.ts:45