add happyTerminal.theme.bash

[mlibre]

Title

Add happyTerminal theme

Description

I've added a custom theme named happyTerminal for the Bash-it project

Motivation and Context

I hope this theme can enhance the user experience and make the command line environment more enjoyable.

How Has This Been Tested?

I've tested this theme and using it on my own linux (Manjaro)

Screenshots (if appropriate):

Types of changes

• [x] New feature (non-breaking change which adds functionality)

Checklist:

• [x] My code follows the code style of this project.
• [ ] If my change requires a change to the documentation, I have updated the documentation accordingly.
• [x] I have read the CONTRIBUTING document.
• [ ] If I have added a new file, I also added it to clean_files.txt and formatted it using lint_clean_files.sh.
• [ ] I have added tests to cover my changes, and all the new and existing tests pass.