Secure authentication for frontend apps with PKCE

AuthKit now supports Proof Key for Code Exchange (PKCE), a security feature that enables public clients like mobile and single-page apps to authenticate securely. PKCE helps address the challenge of code interception attacks in frontend apps by introducing new parameters such as code verifier, code challenge, and code challenge method. The React SDK abstracts the PKCE nuances while keeping the authentication process secure, requiring only the client ID and API Hostname to be set.