Add Chinese flag

How about this one? I've 'warped' it into 16x12 as the original had dimensions more like 17x11. However I think it's OK - it's really unnoticeable as it's basically just red with a yellow dot at this size.

I'm not sure about exactly how to represent the Chinese languages as you've got Chinese Simplified, Chinese Traditional, and various dialects. My recommendation is simply to use this one flag for everything, because how many sites are going to have Chinese Simplified and Chinese Traditional, and need to differentiate between them? If any does, we can cross that bridge when we come to it.

So this flag will basically just mean "Chinese" to a user.

#324762: Add flags for Chinese and Bulgarian