new: [date] modified in services

Gemfile

@@ -4,3 +4,4 @@ gem "jekyll", "~> 4.1"
 gem "jekyll-environment-variables"
 gem 'jemoji'
 gem 'rouge'
+gem 'jekyll-last-modified-at'

_layouts/service.html

@@ -8,6 +8,7 @@ layout: default
       <div class="service service-single">
         <h1 class="title">{{page.title}}</h1>
         <div class="content">{{content}}</div>
+        <p>Last modified - {% last_modified_at %}</p>
       </div>
     </div>
   </div>