Document alternate build workflow using esy (#1590)
Document alternate build workflow using esy (#1590)

* Document alternate build workflow using esy

Describe what is necessary to build the project with esy after the
opam instructions, with the caveat that it is still experimental.

* Use esy x

* Remove warning about esy interaction with OPAM

let-def/reason,cristianoc/reason,cristianoc/reason,facebook/reason,facebook/reason,let-def/reason,let-def/reason,chenglou/reason,chenglou/reason,chenglou/reason,cristianoc/reason,facebook/reason