Improve the docs

[MylesBorins]

Currently the documentation for jstime is primarily in the readme. As the API expands it will be good to document using rustdoc so we can have something a bit nicer for folks to refer

[bdougie]

Hey, I spent some time playing with the runtime to think of a more expanded "hello world," and came up with this idea of running a function that setTimeout for 1000ms. In node on my 8 core macbook pro it takes between 2000-3000ms to run. With the deno runtime, it takes 1003ms to run. I think leveraging that example in the jstime docs would be helpful in new folks getting the context of it.

I haven't quite wrapped my brain around how to do that in Rust. Also, setTimeout is also not written in jstime, but curious if there are plans for that or something similar. I will keep thinking through this but thought I would share my intentions for assisting with the docs.

var start = new Date()
var simulateTime = 1000

setTimeout(function (argument) {
  // execution time simulated with setTimeout function
  var end = new Date() - start
  console.info('Execution time: %dms', end)
}, simulateTime)

[MylesBorins]

Did some quick research on what would be needed to implement some basic timers and opened an issue -> #50