Add rubocop-performance gem

Author: biow0lf

Gemfile

@@ -9,6 +9,7 @@ gem "rspec"
 gem "simplecov", require: false
 gem "standard", require: false
 gem "rubocop", require: false
+gem "rubocop-disable_syntax", require: false
+gem "rubocop-performance", require: false
 gem "rubocop-rake", require: false
 gem "rubocop-rspec", require: false
-gem "rubocop-disable_syntax", require: false

Gemfile.lock

@@ -156,6 +156,7 @@ DEPENDENCIES
   rspec
   rubocop
   rubocop-disable_syntax
+  rubocop-performance
   rubocop-rake
   rubocop-rspec
   simplecov