More docs

[nickchecan]

This pull request updates documentation and dependencies for the project. The main improvements include referencing a full agent example in the documentation and updating the model-mux package version in the example agent.

Documentation improvements:

• Added a link in the README.md to the examples/my-agent directory, which provides a complete example of a Google ADK agent using Model-Mux.

Dependency updates:

• Updated the model-mux dependency in examples/my-agent/package.json from version ^1.0.4 to ^1.0.6.