fix: typo

episodes/introduction.md

@@ -78,7 +78,7 @@ A research software paper should provide a **concise introduction** to your code
 
 For more information about writing these papers, which is beyond the scope of this course, please read [Ten simple rules for writing a paper about scientific software](https://doi.org/10.1371/journal.pcbi.1008390) by Joseph Romano.
 
-:::: spoilers
+:::: spoiler
 
 ### Software journals