* Fix doctests
* Regenerate haskell-ci with config
- use latest haskell-ci
- configure haskell-ci to use doctest
* Update tested with compiler
- update cabal tested-with field
- update .mergify.yaml to new compiler
- restore note about mergify in haskell-ci
This change configures the mergify bot so that:
- PR are validated with the tip of the project before merge
to prevent incompatible PRs to be merged at once which could
break the CI.
- PR maintainer uses a consistent smart squash workflow