Add note about title casing to style guide

_episodes/06-style-guide.md

@@ -183,4 +183,16 @@ Please label links with meaningful texts, in order to [improve
 accessibility](https://webaccess.berkeley.edu/ask-pecan/click-here). Please avoid
 `click here` or similar.
 
+## Title Casing
+
+Lesson and episode titles should be written in title case e.g.
+
+> Saving the World, One Commit at a Time
+
+An exception should be made where the title includes the name of a tool/library/command that must be typed in lower case when used, e.g.
+
+> Data Visualisation with `matplotlib`
+
+(In HTML files, such as the workshop schedule and syllabus files in the [workshop webpage template](https://github.com/carpentries/workshop-template), tool/command/library names such as `matplotlib` in the example above can be correctly formatted using `<code></code>` tags.)
+
 {% include links.md %}