[docs] Adding cli start command

[fellyph]

This pull request significantly improves the documentation for the Playground CLI by clarifying the differences between the new simplified start command and the advanced server command, updating usage instructions, and providing more details on data persistence and configuration options. The documentation now better guides users on when and how to use each command, highlights automatic project mounting and persistence, and introduces new CLI arguments.

Key documentation improvements:

Command Usage and Behavior

• Added a clear explanation of the two main commands, start (simplified, auto-detects project, persists sites, opens browser) and server (advanced, full manual control) in the CLI overview.
• Updated the Quickstart and usage instructions to recommend start for most users, including examples of automatic project mounting and browser launching.
• Clarified the behavioral differences between start and server, especially regarding auto-login, browser opening, and project mounting.

Data Persistence

• Added detailed documentation on how data persistence works in both start and server modes, including the location of persisted files and databases, and the effect of explicit mounts. [1] [2]
• Documented the --reset flag for start mode, explaining how to reset the persisted site and how to manually clear data for server mode. [1] [2]

CLI Arguments and Requirements

• Updated the required Node.js version from 20.18+ to 22.12+ to reflect current recommendations.
• Added documentation for the new --experimental-unsafe-ide-integration argument for Xdebug integration with VS Code and PhpStorm.
• Clarified available arguments for both start and server commands, highlighting the dedicated --reset argument for start.

These changes make the CLI documentation more accurate, user-friendly, and up-to-date for both new and advanced users.