fixup: Add interface for filesize options object

[aitk]

This will provide consistency between filesize and partial function options.

This will also fix an issue I had while utilising the library where I want to validate the options supplied to a generic formatter function for example here is my implementation.

interface SomeNumberOptions = {
   compact: bool
}

const getFormatter = (type: string): (value: any, options: SomeNumberOptions | FileSizeOptions) => string {
    const formatters = {
         number: (value: number, options: SomeNumberOptions): string => {...}
         bytes: (value: number, options: FileSizeOptions): string => {...}
    }

    return formatters[type]
}

I've also updated some options from strings to unions.

[avoidwork]

This is 10.0.8