Added WordPress.gitattributes file

The main purpose of this pull request is to add the **WordPress.gitattributes** file. Please add it to your repository.

I've also made a small change to the project's main **.gitattributes** file (to specifically consider the **.gitignore** file as text). However, this change is not important for the main project. *" * text=auto "* should handle it automatically, but I like my settings clean. So you may or may not consider including this change, it's up to you.