Update critical file(s) according to Chirpy v5.2.1

Gemfile

@@ -2,7 +2,7 @@
 
 source "https://rubygems.org"
 
-gem "jekyll-theme-chirpy", "~> 5.2", ">= 5.2.0"
+gem "jekyll-theme-chirpy", "~> 5.2", ">= 5.2.1"
 
 group :test do
   gem "html-proofer", "~> 3.18"

_config.yml

@@ -185,6 +185,7 @@ exclude:
   - '*.gemspec'
   - tools
   - README.md
+  - CHANGELOG.md
   - LICENSE
   - gulpfile.js
   - node_modules