These templates live under the top level _includes/ directory. Here is what is available:

{%include troubleshooting.html content="
Troubleshooting block.
" %}

{%include note.html content="
Note block.
" %}

{%include info.html content="
Info block.
" %}

{%include important.html content="
Important block.
" %}

{%include question.html content="
Question block.
" %}

{%include ahead.html content="
Thinking ahead block
" %}

{%include warning.html content="
Warning block
" %}

Note - if you want to include a link inside a highlight block that opens in a new window, you will need to use actual html, like:

<a href=\"https://tomcat.apache.org/tomcat-8.0-doc/config/realm.html\" target=\"_blank\">

So, for example:

{%include ahead.html content="
Tomcat Realms:
A <a href=\"https://tomcat.apache.org/tomcat-8.0-doc/config/realm.html\" target=\"_blank\">realm</a> element represents a database of usernames, passwords, and roles (similar to Unix groups) assigned to those users.
" %}

looks like: