feat(examples|docs): cluster proxy/agent examples

[ShookLyngs]

Changes

• Added ClusterProxy and ClusterAgent related code in secp256k1 examples
• Rewrote composed-api doc and part of the demos/examples doc
• Refactored all other examples

Checklist

• [ ] Merge #45
• [ ] Reset base branch to beta

[ShookLyngs]

Are there plans to set up tests using Github Actions?

No plans for examples/docs tests right now. Will have tests for the sdk tho, please follow the issue: #47