docs: Add AdaL to supported coding agents

[liyin2015]

Summary

Adds AdaL to the list of supported coding agents in the description.

About AdaL

AdaL is a self-evolving AI coding agent with:

• Native MCP server support (compatible with all MCP servers)
• Claude Code skills/plugins compatibility
• Advanced agentic capabilities for research and software engineering

Links:

• Website: https://sylph.ai/
• Docs: https://docs.sylph.ai/
• Discord: https://discord.com/invite/ezzszrRZvT

🌸 Generated with AdaL

[google-cla]

Thanks for your pull request! It looks like this may be your first contribution to a Google open source project. Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

View this failed invocation of the CLA check for more information.

For the most up to date status, view the checks section at the bottom of the pull request.