Separate CSSDeclaration from lib.dom.d.ts into a new file lib.css.d.ts

[danmarshall]

This isn't an issue but an idea I wanted to ask about.
I have a project where I want to use only the CSSStyleDeclaration type but not DOM types. I understand that I can just copy-paste into my own .d.ts file, but wanted to ask if there is value in doing this for TypeScript lib itself. One potential value add is that people may refer to a specific CSS implementation, like CSS2 or CSS3.

[mhegazy]

We would like to limit the maintenance cost of the library. currently we generate the CSS declaration the same way we do the rest of the DOM APIs; splitting them into a different file would make the update process harder.

I would recommend copying the parts you need.