fix: Gemfile & Gemfile.lock to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-RUBY-FARADAY-15253521

Author: snyk-bot

Gemfile

@@ -1,5 +1,5 @@
 source "https://rubygems.org"
 
-gem 'github-pages', '>= 201'
+gem 'github-pages', '>= 203'
 gem 'html-proofer', '>= 3.13.0'
 gem 'tzinfo-data', platforms: [:mingw, :mswin, :x64_mingw]