Add admonitions

school.md

@@ -93,6 +93,17 @@ Some of the unique functionalities of `graph-tool` include:
 1.  Support for writing custom [C++
 extensions](https://graph-tool.skewed.de/static/doc/demos/cppextensions/cppextensions.html#cppextensions).
 
+<style>
+blockquote.info {
+  @extend .alert-info;
+}
+blockquote.info p:before {
+  content: "ⓘ Important information ";
+  font-weight:bold;
+  font-size:16px;
+}
+</style>
+
 > In this interactive workshop we will briefly cover the basic and some of the
 > more advanced functionalities of the library. Participants will be given some
 > hand-on exercises which will be discussed during the session.
@@ -102,6 +113,7 @@ extensions](https://graph-tool.skewed.de/static/doc/demos/cppextensions/cppexten
 >    [https://hub.skewed.de](https://hub.skewed.de)
 >
 > and open the notebook from [here](https://hub.skewed.de/hub/user-redirect/git-pull?repo=https%3A%2F%2Fgithub.com%2Fcount0%2Fgt-nascol&urlpath=lab%2Ftree%2Fgt-nascol%2Fgt-workshop.ipynb&branch=master).
+{:.info}
 
 ### igraph