Bump rubocop from 1.12.1 to 1.13.0

Bumps [rubocop](https://github.com/rubocop/rubocop) from 1.12.1 to 1.13.0.
- [Release notes](https://github.com/rubocop/rubocop/releases)
- [Changelog](https://github.com/rubocop/rubocop/blob/master/CHANGELOG.md)
- [Commits](https://github.com/rubocop/rubocop/compare/v1.12.1...v1.13.0)

Signed-off-by: dependabot[bot] <support@github.com>

Gemfile

@@ -52,7 +52,7 @@ end
 group :development, :test do
   gem 'byebug'
   gem 'listen'
-  gem 'rubocop', '~> 1.12', require: false
+  gem 'rubocop', '~> 1.13', require: false
 end
 
 group :test do

Gemfile.lock

@@ -179,7 +179,7 @@ GEM
       mimemagic (~> 0.3.0)
       terrapin (~> 0.6.0)
     parallel (1.20.1)
-    parser (3.0.0.0)
+    parser (3.0.1.0)
       ast (~> 2.4.1)
     pg (1.2.3)
     puma (5.2.2)
@@ -234,12 +234,12 @@ GEM
     regexp_parser (2.1.1)
     reverse_markdown (2.0.0)
       nokogiri
-    rexml (3.2.4)
+    rexml (3.2.5)
     rspec-expectations (3.10.1)
       diff-lcs (>= 1.2.0, < 2.0)
       rspec-support (~> 3.10.0)
     rspec-support (3.10.1)
-    rubocop (1.12.1)
+    rubocop (1.13.0)
       parallel (~> 1.10)
       parser (>= 3.0.0.0)
       rainbow (>= 2.2.2, < 4.0)
@@ -356,7 +356,7 @@ DEPENDENCIES
   rails-dom-testing (~> 2.0.0)
   rails_autolink
   rspec-expectations
-  rubocop (~> 1.12)
+  rubocop (~> 1.13)
   sanitize (~> 5.2)
   sassc-rails (~> 2.1.2)
   simplecov