Update README with info on runtime (#194)

* Update README with info on runtime

* Fix typo

* Fix typos, Improve tone

README.md

@@ -8,7 +8,7 @@ A note writing application for teaching and sharing ReasonML code with inline ev
 
 ## How does it work?
 
-This project uses [rtop-evaluator](https://github.com/Sketch-sh/rtop-evaluator) for evaluating the input
+This project uses [rtop-evaluator](https://github.com/Sketch-sh/rtop-evaluator) for evaluating the input. The evaluator loads refmt & js_of_ocaml compiler as a web worker in the browser. We're not using BuckleScript since it currently doesn't support toplevel evaluation. That means BuckleScript modules like `Js` are not available, and instead one has to run functions from the OCaml stdlib like `print_string`. Belt however works well with js_of_ocaml and support is coming soon!
 
 ## Contributions