functions to make clojure's comparison functions work for Temporal entities

A partial port of tick.core, but now backed by Chronosral on js runtime.

If a function from tick is implemented in this ns then it works the same as the tick equivalent.

The reason that tick has been ported is that it is a popular date/time library. As well as having a different basis on JS runtimes,
there are some philosophical differences between tick and chronos. 

What is there to choose between chronos.tick and chronos?

1. chronos has no zero-arg 'deref' functions. Similarly, there are no functions that make implicit use of
the 'current' or 'ambient' zone. For this reason, there is no `with-clock` macro in chronos

2. chronos is sometimes more verbose - for example to get the year of an Instant for example first requires converting to a zdt by explicitly supplying a zone.

3. in tick the same function is used for parsing strings and accessing properties. For example in tick `(t/date x)` will parse x if it is a string,
or access the date from x if it is e.g. a zdt.

4. chronos blocks non-commutative operations by default (e.g. 'adding' a month to a date)          

Other differences:

* Unlike tick, no entity for year or month exists in chronos - where needed, numbers are used to repsesent those
* Entities for temporal-amounts are alpha - so not included here yet
* No parsing or formatting of non-ISO strings - since this is not in Temporal
* Although there is a timezone entity, functions that would accept or return a timezone instead accept or return a string
* There are no offset-datetime or offset-time entities since they don't exist in Temporal.