Update atomic_doc_template.md.erb

- replace html tags with markdown formatting
- adjust heading/subheading levels for structural integrity

these will permit better handling and display downstream on atomicredteam.io

atomic_red_team/atomic_doc_template.md.erb

@@ -1,11 +1,11 @@
 # <%= technique['identifier'] %> - <%= technique['name'] -%>
 
 ## [Description from ATT&CK](https://attack.mitre.org/techniques/<%= technique['identifier'].gsub(/\./, '/') %>)
-<blockquote>
 
-<%= technique['description'].gsub("%\\<", "%<").gsub(/<code>.*?<\/code>/) { |match| match.gsub('~', '\~') } %>
-
-</blockquote>
+<% attack_description_lines = technique['description'].gsub("%\\<", "%<").gsub(/<code>.*?<\/code>/) { |match| match.gsub('~', '\~') } %>
+<% attack_description_lines.each do |desc_line| %>
+> <%= desc['line'].strip %>
+<% end %>
 
 ## Atomic Tests
 <% atomic_yaml['atomic_tests'].each_with_index do |test, test_number| -%>
@@ -14,9 +14,9 @@
 <% end %>
 
 <% atomic_yaml['atomic_tests'].each_with_index do |test, test_number| -%>
-<br/>
 
-## Atomic Test #<%= test_number+1 %> - <%= test['name'] %>
+
+### Atomic Test #<%= test_number+1 %> - <%= test['name'] %>
 <%= test['description'].strip -%>
 
 
@@ -95,5 +95,4 @@ end%>
 
 
 
-<br/>
 <%- end -%>