gitignore: artifacts

Dependencies

• [2] WQKS2RCV Ignore 'nix develop' outputs directory
• [*] GBCPEGYC Add a .gitignore

Change contents

• edit in .gitignore at line 38
  [2.8]
  + config

  + stamp-h1

  + src/hydra-evaluator/hydra-evaluator

  + src/hydra-queue-runner/hydra-queue-runner