[WIP] Update the refmt contract

[pedrobslisboa]

WIP

This branch was tested with yarn link as we still need to merge this branch: jchavarri/astexplorer-refmt#1

Description

This PR updates the refmt contract for ocaml and reason

How to test it

• Clone mine astexplorer-remt fork: https://github.com/pedrobslisboa/astexplorer-refmt
• Checkout to this branch: feat/pp_ast_ppxlib
• In website folder of astexplorer, call yarn link <path-to-astexplorer-refmt>.
• Follow the readme steps normally
• At localhost, access the ocaml and reasonml and check that it show the ppxlib AST strucutre