Add note about boost:update command requirements

[bjoernzosel]

This PR adds a helpful note in the "Keeping Guidelines Up-to-Date" section to clarify the requirements for the boost:update command.

Changes

• Added a note block explaining that users need to be on the latest Laravel Boost version
• Clarified that Laravel Boost only registers when BOOST_ENABLED=true or APP_DEBUG=true is set in .env

Why

This helps users troubleshoot issues when the boost:update command is not appearing in their artisan command list.

Fixes #352

[pushpak1300]

Thanks for your pull request!

Unfortunately, I'm going to delay merging this code for now. To preserve our ability to adequately maintain this package, we need to be very careful regarding the amount of code we include.