Add installation instructions

[zeFresk]

Maybe you could add instruction about installation in your readme.

It would help noob like me.

(And required packages)

[arxaqapi]

Good idea, will add them

For the moment you can install ocaml 🐫 packages that are published on the OCaml Package Manager using opam.
Be sure to have opam installed and then just:

opam install ojo

You should be good to go afterwards