Mark ky.create() options as optional in public types

[dirkluijk]

Just a small tweak on the ky.create(). I know it's also possible to use the global ky instance, but just in case one wants to use this factory method instead.

[sholladay]

This actually makes the types more consistent because the create() options are already marked optional here:

ky/source/index.ts

Line 19 in a7e2736

ky.create = (newDefaults?: Partial<Options>) => createInstance(validateAndMerge(newDefaults));

Thanks!