Port string-parsers syntax guide to this repo

[JordanMartinez]

In my effort for doing JordanMartinez/purescript-jordans-reference#472, I would like to port the following file to this repo:

• Syntax, which covers the main API here and a general idea for how it works.

What issues, if any, would arise if I do this?

[thomashoneyman]

Would you want to add this to the README or just move the file here directly?

[JordanMartinez]

Since this repo's ReadMe doesn't include anything else, probably just the ReadMe. Then, it will appear both on the ReadMe and in its Pursuit docs