Add js-joda

Would you accept a PR that adds js-joda? If so, I could create one.

js-joda is an immutable date and time library for JavaScript that is very close to the java.time API. It is not just a wrapper around the native Date object, like most other libraries. The API has a domain-oriented design with classes for each of the different use cases, such as LocalDate, ZonedDateTime or Period. Actually, it is quite similar to the upcoming javascript temporal proposal.