Update docs/project_organization/directory_structure.mdx

Co-authored-by: Timothy Divoll <[email protected]>

docs/project_organization/directory_structure.mdx

@@ -171,7 +171,8 @@ A [trial](https://www.jspsych.org/7.3/overview/timeline/#a-single-trial) is the
   :::
 - `introduction.js` displays a message to the user welcoming them to the experiment. They must click on a button to continue.
 - `name.js` displays the name of the task to the user.
-- `startCode.js` emits a start code to a photodiode spot and audible beep
+- `startCode.js` emits a start code to a photodiode spot and audible beep.
+
 - `survey.js` contains trials pertaining to a survey/quiz for the user to complete.
 
 ### lib/