feat(#1): add testing

[AlejandroSuero]

Description

Please include a summary of the change and which issue is fixed. Please also
include relevant motivation and context

Fixes #1 (issue)

• Added jest testing library.
• Ensure action runs
• Ensure selene command runs
• Ensure selene <args> runs
• Ensure selene takes selene.toml into account

Type of change

Please delete options that are not relevant.

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

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide
instructions so we can reproduce. Please also list relevant details about your configuration

• Using jest and the script command npm run test

Configuration:

• Node version (node -v): v20.12.2
• Operating system and version: MacOS 14.4.1

Checklist

• My code follows the style guidelines of this project (eslint, prettier)
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation