Configure rubocop

Use rubocop-rspec for added checks specific to rspec tests.

The two checks that are disabled are pretty annoying in the context of
puppet tests.

.rubocop.yml

+---
+require: rubocop-rspec
+AllCops:
+  DisplayCopNames: true
+  TargetRubyVersion: '2.7'
+  NewCops: enable
+  Exclude:
+  - pkg/**/*
+  - spec/fixtures/**/*
+  - ".vendor/**/*"
+  - vendor/**/*
+Style/FrozenStringLiteralComment:
+  Enabled: false
+Style/MixinUsage:
+  Enabled: false

Gemfile

@@ -14,6 +14,7 @@ group :development, :test do
   gem 'rspec-hiera-puppet'
   gem 'rspec-puppet'
   gem 'rubocop'
+  gem 'rubocop-rspec'
 end
 
 group :docs do

Gemfile.lock

@@ -127,6 +127,11 @@ GEM
       unicode-display_width (>= 2.4.0, < 3.0)
     rubocop-ast (1.28.0)
       parser (>= 3.2.1.0)
+    rubocop-capybara (2.17.1)
+      rubocop (~> 1.41)
+    rubocop-rspec (2.19.0)
+      rubocop (~> 1.33)
+      rubocop-capybara (~> 2.17)
     ruby-progressbar (1.13.0)
     ruby2_keywords (0.0.5)
     scanf (1.0.0)
@@ -149,6 +154,7 @@ DEPENDENCIES
   rspec-hiera-puppet
   rspec-puppet
   rubocop
+  rubocop-rspec
 
 BUNDLED WITH
    2.3.15