Update pull_request_template.md

Author: emilykl

.github/pull_request_template.md

@@ -5,17 +5,17 @@ Please complete each section below.
 -->
 
 ## Link to issue
+<!-- Link to the issue closed by this PR. If the issue doesn't exist yet, create it. -->
 
-Closes (#)
+Closes #(issue number)
 
 ## Description of change
-
-(1-2 sentences)
+<!-- Provide a clear 1-2 sentence description of what this PR does. -->
 
 ## Demo
 
-(Include screenshot or screen recording)
+<!-- Include screenshots or screen recordings of this PR in action. -->
 
 ## Testing strategy
 
-(1-2 sentences explaining tests added or changed, or why testing changes are not needed)
+<!-- Provide 1-2 sentences explaining tests added or changed by this PR. If testing changes are not needed, explain why. -->