Add .gitattributes

Add .gitattributes file to normalize line endings.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@iki.fi>
Normalize all the line endings

Normalized all the line endings with:

git rm --cached -r .
git reset --hard
git add .
git commit -m "Normalize all the line endings"

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@iki.fi>