Inconsistency on Vulkan Format enum

# Summary of feature
Currently there's a small inconsistency on the Format enum names. The snorm formats have the `N` capitalized, so they are `SNorm`, while the unorm ones aren't.

Example:
```
B8G8R8A8Unorm
B8G8R8A8SNorm
```
I propose changing them to:
```
B8G8R8A8Unorm
B8G8R8A8Snorm
```
So basically, changing `SNorm` to `Snorm`.
For consistency. I hope it's not too late to do this kind of breaking change on the library.