Move important functions first

[cprussin]

I just realized that having the most important function (createServer) last makes the docs crazy hard to read. This PR just moves the createServer function to the top of the file, so it's the first function in the docs for Node.HTTP.Secure.

[hdgarrood]

Funnily enough I was just working on addressing this in the compiler: purescript/purescript#3003

Anyway 👍, although perhaps it would make sense to have createServer before SSLOptions too?

[cprussin]

I agree, done, thanks

[hdgarrood]

Thanks!