add .gitattributes file (line ending, ...)

Define the line ending behavior of the different file extensions

Documentation:

• https://git-scm.com/book/fr/v2/Personnalisation-de-Git-Attributs-Git

Examples:

• https://github.com/alexkaratarakis/gitattributes
• https://gist.github.com/Voonder/d5f638b60ca8456691dfa1c6412a264e