docs(readme): add HeatPump MCP Server to third-party list

[jiweiqi]

No source code or build artifacts are introduced—this is purely a documentation change so that users can discover and integrate the HeatPump MCP Server.

Server Details

• Server: HeatPump
• Changes to: README.md only (documentation)

Motivation and Context

Including HeatPump in the official community list increases visibility for users looking for HVAC-focused tools and ensures consistent discovery alongside other third-party MCP servers.

How Has This Been Tested?

• Verified rendered Markdown locally—link and formatting display correctly.
• Confirmed alphabetical ordering to avoid merge conflicts.
• Ran repository markdown linter (npm run lint:md) to ensure style compliance (passes).

Breaking Changes

None. No client configurations or server interfaces are affected.

Types of changes

• Bug fix
• New feature
• Breaking change
• Documentation update

Checklist

• I have read the MCP Protocol Documentation
• My changes follow MCP security best practices (N/A for docs, but no sensitive info added)
• I have updated the server's README accordingly (entry contains description & maintainers)
• I have tested this with an LLM client (N/A for docs)
• My code follows the repository's style guidelines (Markdown style/lint passes)
• New and existing tests pass locally (N/A)
• I have added appropriate error handling (N/A)
• I have documented all environment variables and configuration options (N/A)

Additional context

HeatPump provides a suite of residential HVAC calculators that leverage MCP to expose its sizing, cost-estimation, and cold-climate verification tools via secure, agent-friendly APIs. The link helps builders quickly discover these capabilities without requiring a full source contribution.

[olaservo]

Thanks for your contribution to the servers list. This has been merged in this combined PR: #2370

This is a new process we're trying out, so if you see any issues feel free to re-open the PR and tag me.