Add generic to Reference.create()

[florianeckerstorfer]

The create() method in Reference.ts was missing the generic, which caused a type error in the following example

yup
  .object({
    availableFrom: yup.number(),
    availableTo: yup
      .number()
      .moreThan(yup.ref('availableFrom')),
  });

Error:

Argument of type 'Reference<unknown>' is not assignable to parameter of type 'number | Reference<number>'.

In this PR I add a generic to the create() method and type Reference and ReferenceOptions with it.

[jquense]

thanks!

[dschaller]

Is this fix going to be available in 0.38.x?