Onboard SIG: MCP Server

### SIG Name

MCP Server

### Assignee

austinlparker

### Project Proposal PR

https://github.com/open-telemetry/community/pull/3128

Blog post https://github.com/open-telemetry/opentelemetry.io/pull/8331 

### Onboarding Checklist

- [ ] Project Board
- [ ] Add Meeting Times, GC Liaison, Slack Channel, Google Doc to sigs.yml
- [ ] SIG Slack Channel
- [ ] GitHub Teams