Add support to handle sensitive information (tokens...)

[UlisesGascon]

Main Changes

• Add utility to check GITHUB_TOKEN, this will be use to retrieve data from the API later on (5de12f4)
• Add information on how to handle secrets (fc28ad2)

Changelog

• 5de12f4 feat: add utility to check GITHUB_TOKEN by @UlisesGascon
• fc28ad2 docs: add information on how to handle secrets by @UlisesGascon