Add --init option to get you started quickly

[Chemaclass]

📚 Description

Right now, we have documented how to start with bashunit step by step (see: https://bashunit.typeddevs.com/quickstart#usage), but I thought we could simplify even more with an --init option to create the initial setup and faster "onboarding" 🚀

🔖 Changes

• Added a new initialization command that introduces a --init option for faster project setup
• Created an initialization script that prepares a bootstrap file and sample test for newcomers
• Documented the new --init option in the command-line guide
• Implemented an acceptance test validating that the initialization command generates the expected files

✅ To-do list

• I updated the CHANGELOG.md to reflect the new feature or fix
• I updated the documentation to reflect the changes