adds boy scout rule to motivation

basics.html

@@ -141,7 +141,18 @@
             - (done right) decision based on regression testing
           </section>
 
-          <section id="motivation-collaboration" data-markdown>
+          <section id="motivation-collaboration-1" data-markdown>
+            ## motivation #3
+
+            ![boy scout rule](img/boy-scout-rule.jpg)
+
+            notes:
+            - there's a rule in open source software ...
+            - at least open issue
+            - if trivial to fix: do it!
+          </section>
+
+          <section id="motivation-collaboration-2" data-markdown>
             ## motivation #3
             ### collaboration made easy