[specs] Auth API Beta

[chadyj]

Auth API is a lightweight API to verify wallet address ownership for web3 use cases such as SIWE.

This issue continues the alpha work, incorporates developer feedback, improves documentation, and polishes the SDK.

• [x] Project brief

Requires

• [ ] https://github.com/WalletConnect/walletconnect-docs/issues/253

Main features

• Domain binding
• Support EIP-1271
• Pairing API integration

Implementation

• [ ] JS
• [ ] Swift
• [ ] Kotlin