Copyright's update

1. Install the headroom tool. You can get it from the sources:

   hit clone vaclavsvejcar/headroom
   cd headroom
   cabal build

2. Summoner already has the configurations and template files for the headroom tool. Modify it if needed:
   • .headroom.yaml
   • headroom-templates/haskell.mustache
3. Run to update copyrights:

   headroom run

4. Check the diff on the correct updates:

   hit diff