Add links to slack mcp by Zencoder

[alexs-forgood-ai]

Description

Server Details

• Server: Slack
• Changes to: added Streamable HTTP support and token authentication. Maintaining the old archived version of the Slack server https://github.com/modelcontextprotocol/servers-archived/tree/main/src/slack

Motivation and Context

Adds new functionality, improves some tool descriptions for better understanding by LLM. Also adds unittests

How Has This Been Tested?

Tested with Zencoder as a client. Used internally for several weeks now. All of the tool functionality is preserved and/or improved

Breaking Changes

Yes, new link to the server, otherwise for stdio transport there are no interface 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