Add gemspec

rubocop-github.gemspec

@@ -0,0 +1,20 @@
+Gem::Specification.new do |s|
+  s.name = "rubocop-github"
+  s.version = "0.0.0"
+  s.summary = "RuboCop GitHub"
+  s.description = "Code style checking for GitHub Ruby repositories "
+  s.homepage = "https://github.com/github/rubocop-github"
+  s.license = "MIT"
+
+  s.files = Dir["README.md", "LICENSE", "lib/**/*.rb"]
+
+  s.add_dependency "rubocop", "~> 0.46"
+
+  s.add_development_dependency "minitest", "~> 5.10"
+  s.add_development_dependency "rake", "~> 12.0"
+
+  s.required_ruby_version = ">= 2.3.0"
+
+  s.email = "engineering@github.com"
+  s.authors = "GitHub"
+end