feat: working farcaster client with neynar

[sayangel]

Relates to:

Farcaster client: https://github.com/ai16z/eliza/issues/300 Modification of open PR: https://github.com/ai16z/eliza/pull/386

Risks

Low

Background

What does this PR do?

Adds a farcaster-client package so that Eliza agents can post to Farcaster. This PR modifies an existing Farcaster client PR to use Neynar instead of a direct hub. This makes it easier for people to deploy hubs and makes it easier to add additional features in the future using Neynar's APIs for interacting with Farcaster data.

What kind of change is this?

Features (non-breaking change which adds functionality)

Documentation changes needed?

Needs documentation on how to create a signer that can submit messages to Farcaster (via Neynar).

Testing

I have tested this PR by running a local eliza agent that is making posts on Farcaster via the Yoinker account: https://warpcast.com/yoinker

All the accounts in this cast have been created by a local Eliza instance.

Where should a reviewer start?

• Populate the new Farcaster env variables
• Add "farcaster" client to your character
• Run the agent
• Verify that a cast is made on startup

Detailed testing steps

[rubinovitz]

Thanks! Neynar is The Way.

[bmgalego]

can you include #386 so it adds my commits too