docs: fix typos for unit 1

[pabroux]

Hello there 👋🏻,

I've noticed some typos in the unit 1. More precisely I've changed the following files:

• hf-mcp-server.mdx (e.g., advanatage → advantage)
• gradio-mcp.mdx
• mcp-clients.mdx (I added a tip callout for a tip to keep it consistent with the other tip style in the same document)

[pabroux]

@burtenshaw is this repo still active? I saw the last commit is 4 month old.

I can help you (i.e., Hugging Face) maintain it. For instance, in MCP client in unit 1, mcp.json configuration seems to only be valid for VS code now. The standard structure has changed since it was written (e.g. mcpServers field instead of servers).