Sign In With Farcaster (SIWF) Plugin for Better Auth

The `better-auth-siwf` package provides a plugin for the `better-auth` framework, enabling users to authenticate via Farcaster identities. It mirrors the developer experience of the official Sign In With Ethereum (SIWE) plugin, adapting the authentication flows and schema for Farcaster. This plugin handles the server-side verification of Farcaster Quick Auth JWTs, establishes Better Auth session cookies, and can optionally resolve enriched Farcaster user data via a provided callback (e.g., from Neynar API). The current stable version is 1.0.28. While a specific release cadence isn't stated, the 1.0.x versioning suggests a focus on stability with incremental improvements. Its key differentiator is its seamless integration with the `better-auth` ecosystem, offering a standardized approach to Farcaster authentication within that framework.