docs: create comprehensive SuperClaude quickstart guide

[mithun50]

This commit introduces a new, comprehensive quickstart guide for the SuperClaude framework. The guide is created as superclaude-quickstart.mdx in the content/guides directory.

This guide has been developed iteratively to include:

• A simple 1-2-3 quickstart for installation and basic setup.
• Detailed instructions on how to use SuperClaude with Happy Coder, including common workflow examples.
• An overview of common use cases.
• A list of essential commands.
• A list of available MCP servers.
• A list of the 14 specialized AI agents.
• A list of the 5 behavioral modes.

The guide is written in a beginner-friendly tone and format, following the existing style of the documentation site. It also includes a link to the official SuperClaude GitHub repository for further information.

Additionally, the _meta.ts file has been updated to include the new guide in the documentation navigation.