Add .gitattributes

[fezfez]

This will drop downloaded package size drastically

before : 1749 items, size 4,2 MB
after : 271 items, size 827,5 kB

[stelgenhof]

Thanks! This is great.
There are however some other test related files/folders (e.g. .github, .travis.yml) that can be excluded as well.|
Would you mind adding those as well?

[fezfez]

Ok 👍

[fezfez]

@stelgenhof done and rebase ;)