Add .gitattributes to ensure EOL normalization

[adamvoss]

Add .gitattributes to enforce line ending normalization. Addition was modeled after the .gitattributes inclusion.

[msftclas]

Thank you for your submission, we really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.

❌ adamvoss sign now
_{You have signed the CLA already but the status is still pending? Let us recheck it.}