Improve setup documentation with prerequisites and clearer installation flow

Problem

While setting up Kmesh locally, I noticed that the current documentation can be confusing for new contributors, especially around the installation flow.

Some key challenges:

• Istio dependency is not clearly highlighted before deployment
• The correct setup order is not explicitly defined
• It is unclear how to verify a successful installation
• New users may attempt to run kmesh-daemon directly without a Kubernetes environment

Proposed Solution

I would like to improve the setup documentation by:

• Adding a "Prerequisites" section (including Istio requirement)
• Defining a clear setup flow (Kubernetes → Istio → Kmesh)
• Adding verification steps (e.g., checking running pods)
• Including a "Common Mistakes" section to avoid confusion

Motivation

As a new contributor, I faced these issues during setup. Improving the documentation would make onboarding easier for others and reduce setup friction.

Additional Context

I have successfully set up Kmesh locally and verified the deployment, so I can contribute these improvements based on real experience.

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I would like to work on this issue. Please let me know if this approach looks good.