[Feat]: Please provide documentation for TCK and ITK

### Is your feature request related to a problem? Please describe.

A2A provides TCK and ITK but as a user there is a confusion of what they are & how to use.

### Describe the solution you'd like

A page describing what they are, how are they are useful, when to use, how to use(a mock example)

### Describe alternatives you've considered

Provide information for Agents.md

### Additional context

_No response_

### Code of Conduct

- [x] I agree to follow this project's Code of Conduct

Look for existing documentation files like Agents.md in the repository to understand the current structure. Research what TCK (Test Compatibility Kit) and ITK (Integration Test Kit) are within the A2A project context, possibly by examining test directories or related code. Draft a new documentation page explaining their purpose, usage, and include a mock example, then propose where to add it.

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