Try to use GHCJS

[vrom911]

Okay, guys. I did not succeed in integrating GHCJS to frontend. Here is what I've got so far.

The stopper at the moment is network library — see this issue.

Also, the crucial thing that I have noticed: switching between different type of compilers (ghc and ghcjs) requires to rebuild everything from scratch every time. This is kinda inappropriate and a huge stop sign for me at the moment. I'm building with cabal. Stack doesn't support ghcjs anymore, so the possible solution could be to build the frontend with Stack and backend with Cabal, but, I don't know is this would be good either.

This PR is just to show purposes only.

Build instructions

We have two cabal.project files:

• cabal.project — used by default, builds with ghc compiler (version 8.4 is used in order to be consistent with ghcjs used version). Should be used to build backend (as per plan)
• cabal-ghcjs.project — builds with ghcjs compiler. Should be used to build frontend.

To build backend:

cabal new-build all

To build frontend:

cabal new-build all --project=cabal-ghcjs.project