Add looot third-party MCP plugin (API key header auth)

[walidboulanouar]

looot is a remote MCP server and API with one key and prepaid balance for about 2,500 data endpoints (work email, phone, company enrichment, Google SERP, web pages). This PR adds third_party/looot/ in the same shape as the Hunter and Brevo plugins: mcp.json with an Authorization: Bearer ${LOOOT_API_KEY} header, plugin.json with the LOOOT_API_KEY variable, README, CHANGELOG, LICENSE and logo, plus one entry each in .cursor-plugin/marketplace.json and the README table.

I did not run scripts/validate-plugins.mjs (it needs ajv installed). I checked that both JSON files parse. I work on looot.

---

Note

Low Risk
Additive marketplace plugin and remote MCP wiring only; no changes to core repo logic beyond listing the new integration.

Overview
Adds the looot third-party integration so Cursor agents can call looot’s hosted MCP API for prospecting and enrichment (work emails/phones, company data, SERP/web search, etc.) via a user’s prepaid account.

The new third_party/looot/ package follows the usual integration layout: plugin.json with required LOOOT_API_KEY, mcp.json HTTP server at https://api.looot.ai/mcp with Authorization: Bearer ${LOOOT_API_KEY}, plus README, CHANGELOG, and MIT LICENSE. looot is registered in .cursor-plugin/marketplace.json and the root README plugin table (author looot).

^{Reviewed by Cursor Bugbot for commit af669d8. Bugbot is set up for automated code reviews on this repo. Configure here.}