`FileField`'s `maxFiles` limits only amount of files added at once

[maciek50322]

Describe the bug maxFiles limits only amount of files added with single selection

To Reproduce Steps to reproduce the behavior:

1. Make <FileField multiple maxFiles={1}> ...
2. Add two files at once - rejects both
3. Add one file
4. Add another file
5. Now you have two files (over limit 1)

Expected behavior maxFiles should limit max amount of files added, not just with single selection. Also probably shouldn't reject all of them when selecting more than maxFiles, maybe should accept just enough to fill this amount.