Documentation improvement: Quick start for new contributors

[ErenAri]

Problem statement

To help new contributors understand AegisBPF better with documents

Proposed solution

We should add a short, quick-start section for contributors:

• How to run locally
• How to test policies
• How to submit PRs

This will lower the barrier for community contributions.

Alternatives considered

No response

Risk and compatibility

No response

Readiness checklist

• I checked that this is not already tracked in open issues.
• I can help with implementation and/or testing.