Allow install beta

[Chemaclass]

📚 Description

Closes: https://github.com/TypedDevs/bashunit/issues/210

Currently, the installer tool allows you to install a concrete version, once it was release. However, there is no easy way to benefit of the features/bug-fixes already merged into main unless you download the project and run the build.sh yourself.

🔖 Changes

• Allow using main as [version], to get the main branch and build the "main non-stable" bashunit version.

✅ To-do list

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

[Chemaclass]

Can you help me with the failing test, @Tito-Kati or @khru ? I cannot reproduce it locally (with my MacOS) 🤔

[antonio-gg-dev]

I've fixed the error that the workflows were giving on Linux. By removing the git mock, I could have fixed the mock, but being an acceptance test, it seemed more correct to remove it.

Additionally, I've taken the liberty of applying the corrections I requested myself and making a few more minor changes.