Add lspServers config to clangd plugin

[micahstubbs]

Summary

• Add lspServers configuration to clangd plugin entry in marketplace.json

Fixes #12

Root Cause

Claude Code reads LSP configuration from the lspServers field in marketplace.json, not from .lsp.json files in plugin directories.

Test Plan

• Install/update the clangd plugin
• Restart Claude Code session
• Verify LSP works on .c/.cpp/.h/.hpp files

[bl-ue]

@shyney7 I see you've reacted to this PR; are you able to help me understand the value of it? I'm not aware of .lsp.json not being used, and no one has really complained about these LSPs not working as they're currently configured. I'm totally fine with fixing them if there's a problem, but I'd like to understand the need first. This PR adds a lspServers field to marketplace.json, but the contents of that lspServers field are already in the clangd plugin's .lsp.json, so this would result in duplication.

[jeong-sik]

Friendly ping — any feedback on this? Happy to adjust if needed.