Update Frames guide with frame-react package

[gskril]

Relevant docs updates if farcasterxyz/frames#35 gets merged.

PR-Codex overview

This PR focuses on updating the documentation and code for the Frames v2 SDK integration, enhancing setup instructions, and improving the implementation of components for better clarity and functionality.

Detailed summary

• Updated link in docs/index.md to point to /developers/frames/v2/.
• Added a warning in getting-started.md about video demo being outdated.
• Clarified setup instructions for creating a NextJS app with default config options.
• Updated installation commands to include @farcaster/frame-react.
• Renamed WagmiProvider.tsx to ClientProviders.tsx and included FrameProvider.
• Refactored provider component to use wagmiConfig and FrameProvider.
• Changed demo component name from Demo to Home.
• Simplified context display and improved action button implementations in Home.
• Enhanced wallet connection functionality with clearer button states and error handling.
• Added transaction handling with useSendTransaction and improved UI feedback.
• Incorporated signature methods with useSignMessage and useSignTypedData.

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