added base64 and bigdecimal dependencies

Author: rongxin-liu

jekyll-theme-cs50.gemspec

@@ -12,10 +12,12 @@ Gem::Specification.new do |spec|
   spec.summary = "This is CS50's theme for Jekyll."
   spec.version = "1.1.0"
 
+  spec.add_runtime_dependency "base64"
+  spec.add_runtime_dependency "bigdecimal"
   spec.add_runtime_dependency "deep_merge", "1.2.2"
-  spec.add_runtime_dependency "jekyll", "4.4.1"
+  spec.add_runtime_dependency "jekyll", "4.3.4"
   spec.add_runtime_dependency "jekyll-sass-converter", "2.2.0" # https://github.com/jekyll/jekyll-sass-converter#dropped-support-of-importing-files-with-the-same-filename-as-their-parent-file
-  spec.add_runtime_dependency "sanitize", "7.0.0"
+  spec.add_runtime_dependency "sanitize", "6.1.3"
 
   CS50::PLUGINS.each do |gem, version|
     spec.add_runtime_dependency gem, version