Add filter option

[SimenB]

e.g.

cdn-uploader -a foobar --filter "*.jpg" folder

Might be nice to exclude as well

cdn-uploader -a foobar --exclude "*.json" folder

[ivarconr]

should we support glob patterns?

[SimenB]

Yup, I think so.

https://github.com/sindresorhus/globby