refactor: update script description and improve output formatting

[manghidev]

This pull request updates the scripts/start.sh file to simplify the LazyVim Docker installation process, improve usability, and remove unnecessary features. Key changes include replacing interactive terminal restart functionality, switching the default branch to main, and streamlining the Docker build process.

Simplification of installation process:

• Removed the interactive terminal restart functionality and associated helper script. Users are now instructed to manually restart their terminal or source their shell configuration file to activate LazyVim commands. [1] [2]

• Replaced the detailed Docker environment setup commands with a single make build command, simplifying the build process and reducing script complexity.

Usability improvements:

• Updated the script's messaging to use echo instead of printf for consistency and readability. This affects informational, success, warning, and error messages throughout the script. [1] [2]

• Enhanced the onboarding instructions by adding a step-by-step guide on how to get started after installation, including terminal restart instructions and the first command to run.

Configuration updates:

• Changed the default branch for installation from develop to main to align with standard practices and ensure stability.closes start.sh script failing to clone repo #16