added avatar plugin

Gemfile

@@ -23,6 +23,7 @@ group :jekyll_plugins do
   gem 'jekyll-toc'
   gem 'jekyll-gist'
   gem 'jekyll-paginate'
+  gem 'jekyll-avatar'
 end
 
 gem "kramdown-math-katex"

_config.yml

@@ -79,6 +79,7 @@ plugins:
   - jekyll-seo-tag
   - jekyll-remote-theme
   - jekyll-paginate
+  - jekyll-avatar
 
 # See https://jekyllrb.com/docs/pagination/
 # For pagination to work, you cannot have index.md at the root of your repo, instead you must rename this file to index.html