ECMA-402 PR Coverage: Add fractionalSecondDigits option

[sffc]

Spec PR: tc39/ecma402#347

According to tc39/ecma402#347 (comment) and the meeting minutes, there are partial tests added in #2194. Please verify if additional tests need to be added.

@FrankYFTang

[sffc]

The following was recorded in the July 2019 ECMA-402 meeting:

Notes: not yet covered in Test262: format , formatToParts , formatRange and formatRangeToParts.

[caiolima]

I can see tests for the following methods:

• format: https://github.com/tc39/test262/blob/master/test/intl402/DateTimeFormat/prototype/formatToParts/fractionalSecondDigits.js
• formatToParts: https://github.com/tc39/test262/blob/master/test/intl402/DateTimeFormat/prototype/formatToParts/fractionalSecondDigits.js
• formatRage: https://github.com/tc39/test262/blob/master/test/intl402/DateTimeFormat/prototype/formatRange/fractionalSecondDigits.js

It seems that the missing version is formatRangeToParts.

[caiolima]

I'm going to work on this to add missing cases for formatRangeToParts.

[rwaldron]

@sffc looks like @caiolima resolved this last winter, so I'm closing the issue now!