Enhance README organization, add more background info to code

[GavinRay97]

Heya,

When I first read the Rune readme, there were a couple of things I thought could be improved:

• I didn't understand where methods like appendMotheredHuman etc come from. We "magically" have access to something we didn't define and it feels strange. It gets described later on, but it would have been nice for a comment to say "Hey, don't worry! I'll explain why this magic-method exists in a little bit!"
• DataDraw doesn't get mentioned, and I had to piece the connection together myself. In my opinion, a HUGE amount of appeal comes from the fact that DD is integrated into Rune, and it's very interesting + explains much of the behavior and design decisions/architecture + performance.

Also, many people will want to jump directly to specific things ("how do I build this?", "show me a code example?") without reading the rest of it, so I tried to add enough context to each section that it would make sense if you went straight there and skipped the rest.

Lastly, I added some organizational structure and a TOC so folks can navigate the page easier.

Hope this is helpful, I'd like to highlight Rune in the best way possible for potential users as I think it has some neat ideas 🙂

---

Ahh, one last thing -- I chose the languages for the syntax highlighting for each code block based on which one looked the best/could highlight the majority of the tokens:

Go:

// Check the MAC (message authentication code) for a message.  A MAC is derived
func checkMac(macSecret: secret(string), message: string, mac: string) -> bool {
    computedMac = computeMac(macSecret, message)
    return mac == computedMac
}

Rust (TypeScript comes close too, but not quite as good):

class Human(self: Human, name: string, mother: Human? = null(self), father: Human? = null(self)) {
  self.name = name
  if !isnull(mother) {
    mother.appendMotheredHuman(self)
  }
}

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[GavinRay97]

Sorry about the random formatting changes that removed only spaces in the diff. VS Code auto-format did that -- I didn't catch it in the PR. I can resubmit if it's an issue.

[GavinRay97]

I just learned about the dataview tool and figured out what it does, it'd be neat to mention that as well in the README!

[waywardgeek]

Thanks for all the work on documentation!