Add dependency on rubocop-packaging

This helps to ensure that parser is cleanly and
easily maintainable in Debian and other downstreams.

Signed-off-by: Utkarsh Gupta <utkarsh@debian.org>

parser.gemspec

@@ -59,4 +59,5 @@ Gem::Specification.new do |spec|
   spec.add_development_dependency 'simplecov', '~> 0.15.1'
 
   spec.add_development_dependency 'gauntlet'
+  spec.add_development_dependency 'rubocop-packaging'
 end