Merge pull request #209 from georgefst/readme-haddock

Mention docs on hover feature in README

README.md

@@ -53,6 +53,24 @@ This is *very* early stage software.
 
  ![Eval](https://i.imgur.com/bh992sT.gif)
 
+- Type information and documentation on hover. Note that currently, in order for docs to be displayed for dependencies, they must have been built with GHC's `-haddock` flag:
+
+ - For cabal:
+ - Add to your global config file (e.g. `~/.cabal/config`):
+ ```
+ program-default-options
+ ghc-options: -haddock
+ ```
+ - Or, for a single project, run `cabal configure --ghc-options=-haddock`
+
+ - For stack, add to global `$STACK_ROOT\config.yaml`, or project's `stack.yaml`:
+ ```
+ ghc-options:
+ "$everything": -haddock
+ ```
+
+ This will cause compilation errors if a dependency contains invalid Haddock markup, though in a future version of GHC (hopefully 8.12), [these will be demoted to warnings](https://gitlab.haskell.org/ghc/ghc/-/merge_requests/2377).
+
  - Many more (TBD)
 
 ## Installation