react function last options

[ahsanghalib]

last two options were optional. but they are not. typescript create error.

yup/src/util/reach.ts

Line 53 in e785e1a

const reach = (obj: {}, path: string, value: any, context: any) =>

[mattywong]

@jquense would you be open to a pr for this?

 const reach = (obj: {}, path: string, value: any, context: any) =>  // before

 const reach = (obj: {}, path: string, value?: any, context?: any) => // after

not sure if the getIn function needs to change (though i would assume it would take the same parameters), but there looks like there's tests in place to already test for when there's only the 2 required arguments for reach.

https://github.com/jquense/yup/blob/master/test/yup.js#L100
https://github.com/jquense/yup/blob/master/test/yup.js#L109

[jquense]

@mattywong sure!