add 21st.dev official MCP

[serafimcloud]

Description

Adding 21st.dev Magic MCP server to the Official Integrations section of the README.

Server Details

• Server:
• Changes to:

Motivation and Context

How Has This Been Tested?

Breaking Changes

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update

Checklist

• I have read the MCP Protocol Documentation
• My changes follows MCP security best practices
• I have updated the server's README accordingly
• I have tested this with an LLM client
• My code follows the repository's style guidelines
• New and existing tests pass locally
• I have added appropriate error handling
• I have documented all environment variables and configuration options

Additional context

Added the following entry to the Official Integrations section. All entries are kept in alphabetical order to minimize merge conflicts.

[dsp-ant]

I do not have access to https://github.com/21st-dev/mcp or it does not exist. I would love to hold back on this until the repository is open.

[dsp-ant]

See comment above

[serafimcloud]

@dsp-ant Sorry, I made a typo in the URL address. I've fixed that.