CLJS implementation

[dm3]

Use js-joda as the javascript impl.

[henryw374]

• [ ] CLJSJS package pull request
• [ ] Good way to access all classes of js-joda. see issue

[henryw374]

Probably incomplete list of the kinds of things that'll need work

• interop syntax (Class/staticMethod not in cljs)
• no extend in cljs
• imports of java.time need alternative to get the js-joda ones
• macros need to move for cljs
• import-vars alternative
• get-fields-of-type alternative