add datetime to deps

Dependencies

• [2] BKOIYITR added some json responses
• [*] SAFVRDTK * Put Hydra's dependencies so that they can easily be installed in a
• [*] DO432JDJ * Build Hydra with the Nix Perl bindings.

Change contents

• edit in deps.nix at line 39
  [2.22]

  [5.327]
  + perlPackages.DateTime