Add RuboCop

.rubocop.yml

@@ -0,0 +1,26 @@
+inherit_from: .rubocop_todo.yml
+
+AllCops:
+  TargetRubyVersion: 2.4
+  NewCops: enable
+
+Layout/FirstArrayElementIndentation:
+  EnforcedStyle: consistent
+
+Style/StringLiterals:
+  EnforcedStyle: double_quotes
+
+Metrics/BlockLength:
+  Exclude:
+    - spec/**/*
+
+Naming/MethodParameterName:
+  AllowedNames:
+    - x
+    - y
+    - id
+    - to
+
+Naming/FileName:
+  Exclude:
+    - 'gemfiles/websocket-driver-*.gemfile'

.rubocop_todo.yml

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+# This configuration was generated by
+# `rubocop --auto-gen-config`
+# on 2020-08-25 19:54:53 UTC using RuboCop version 0.89.1.
+# The point is for the user to remove these configuration records
+# one by one as the offenses are removed from the code base.
+# Note that changes in the inspected code, or installation of new
+# versions of RuboCop, may require this file to be generated again.
+
+# Offense count: 24
+# Configuration parameters: IgnoredMethods.
+Metrics/AbcSize:
+  Max: 66
+
+# Offense count: 5
+# Configuration parameters: CountComments, CountAsOne.
+Metrics/ClassLength:
+  Max: 258
+
+# Offense count: 6
+# Configuration parameters: IgnoredMethods.
+Metrics/CyclomaticComplexity:
+  Max: 14
+
+# Offense count: 35
+# Configuration parameters: CountComments, CountAsOne, ExcludedMethods.
+Metrics/MethodLength:
+  Max: 52
+
+# Offense count: 9
+# Configuration parameters: CountComments, CountAsOne.
+Metrics/ModuleLength:
+  Max: 602
+
+# Offense count: 5
+# Configuration parameters: IgnoredMethods.
+Metrics/PerceivedComplexity:
+  Max: 14
+
+# Offense count: 2
+# Cop supports --auto-correct.
+# Configuration parameters: Keywords.
+# Keywords: TODO, FIXME, OPTIMIZE, HACK, REVIEW
+Style/CommentAnnotation:
+  Exclude:
+    - 'spec/node_spec.rb'
+
+# Offense count: 45
+Style/Documentation:
+  Enabled: false
+
+# Offense count: 7
+# Cop supports --auto-correct.
+# Configuration parameters: EnforcedStyle.
+# SupportedStyles: compact, exploded
+Style/RaiseArgs:
+  Exclude:
+    - 'lib/ferrum/browser/client.rb'
+    - 'lib/ferrum/browser/command.rb'
+    - 'lib/ferrum/browser/process.rb'
+    - 'lib/ferrum/browser/xvfb.rb'
+    - 'lib/ferrum/frame/runtime.rb'