Add README files to integrations missing documentation

What

Two integration packages have no README.md:

• packages/agentmesh-integrations/moltbook/
• packages/agentmesh-integrations/openclaw-skill/

Additionally, 10+ examples across packages are missing README.md or requirements.txt files.

Why

A package without a README is invisible to potential users. Contributors browsing the integrations directory skip packages they can't quickly understand.

How

1. Copy the structure from any existing integration README (e.g., langchain-agentmesh/README.md)
2. For each package, include:
   • One-sentence description of what it does
   • Installation: pip install <package-name>
   • 5-line quickstart example
   • Link to full docs and related integrations
3. Bonus: pick 2-3 examples missing README files and add those too

Acceptance Criteria

• moltbook/README.md created with install + quickstart
• openclaw-skill/README.md created with install + quickstart
• At least 2 example directories get a README.md
• All READMEs follow the existing formatting pattern