Feature parity with built-in Array methods

[katis]

proem/array needs to be able to do at least the same things that built-in Array methods can do, but in an
immutable context. Below is a list of Array methods and functions and if proem already implements their
equivalents. Not all of these make sense in immutable code, so let's discuss about it if you want to start
working on a function.

• Array​.from
• Array​.isArray
• Array​.prototype​.concat
• Array​.prototype​.entries
• Array​.prototype​.every
• Array​.prototype​.fill
• Array​.prototype​.filter
• Array​.prototype​.find
• Array​.prototype​.find​Index (not exported!)
• Array​.prototype​.flat
• Array​.prototype​.flatMap
• Array​.prototype​.for​Each
• Array​.prototype​.includes
• Array​.prototype​.indexOf
• Array​.prototype​.join
• Array​.prototype​.last​IndexOf
• Array​.prototype​.map
• Array​.prototype​.pop (array.drop)
• Array​.prototype​.push
• Array​.prototype​.reduce
• Array​.prototype​.reduce​Right
• Array​.prototype​.reverse
• Array​.prototype​.shift
• Array​.prototype​.slice
• Array​.prototype​.some
• Array​.prototype​.sort
• Array​.prototype​.splice
• Array​.prototype​.unshift

See MDN for more indepth descriptions about the Array methods