Require config in the gemspec

Author: khiga8

erblint-github.gemspec

@@ -8,7 +8,7 @@ Gem::Specification.new do |s|
   s.homepage = "https://github.com/github/erblint-github"
   s.license = "MIT"
 
-  s.files = Dir["README.md", "LICENSE", "lib/**/*"]
+  s.files = Dir["README.md", "LICENSE", "lib/**/*", "config/**/*"]
   s.require_paths = ["lib"]
 
   s.required_ruby_version = ">= 2.7.0"