Bug: type metadata.chromaSubsampling as union with undefined

[DavidVaness]

Hey @lovell,
thanks for the great work on sharp

Right now chromaSubsampling is typed as required.

sharp/lib/index.d.ts

Line 1072 in 2474bd4

chromaSubsampling: string;

Given that all metadata values are a union with undefined, I think this one has been overlooked and needs to be changed to

chromaSubsampling?: string | undefined;

I have created a PR to update the type here
#4191

Feel free to close / delete the PR if the type was correct ✌🏼

[lovell]

v0.33.5 now available, thanks for the PR.