Add LENS B20 skill

[Tholynceus]

Adds the lens-b20 skill by LENS (https://lnsx.io), an on-chain rug-risk scanner for Base.

What it does:

• prepare / deploy B20 tokens (Base's native precompile standard, Beryl)
• validate a config with a live gas + admin-balance check, plus a LENS rug-risk read (CLEAR / CAUTION) before deploy
• read any ERC-20 on Base, check balances, gas, and tx receipts

Notes:

• read-only by default; prepare returns an UNSIGNED tx only, never signs or broadcasts
• no auth / no API key
• backed by a public endpoint: https://lens-liard.vercel.app/api/b20-skill

Folder: lens-b20/ (SKILL.md, catalog.json, scripts/lens.sh, lens-b20.md)