Problem: We want to support code folding for functions and types
in our lsp.
Solution: Add `foldingAST` function that produces an additional
list of ranges along with the given monad used in `haskell-lsp`
API to collect ranges that are consequently sent to server.
Problem: With generated ReasonLIGO grammar we need to develop its
parser as well. With it we also need to restructure AST a bit
and add expressions that are used for ReasonLIGO specifically.
Solution: Add ReasonLIGO parser and some dummy examples of its
usage, adapt AST to it, rename LIGO to AST.
