Minor syntax change (#531)

Co-authored-by: Howard Baek <[email protected]>

action-transfer.Rmd

@@ -482,7 +482,7 @@ demo$deploy()
 
 In this chapter, you've learned how to transfer files to and from the user using `fileInput()` and `downloadButton()`.
 Most of the challenges arise either handling the uploaded files or generating the files to download, so I showed you how to handle a couple of common cases.
-If I didn't cover your specific challenge here, you'll need to apply your own unique creativity the problem 😄.
+If I didn't cover your specific challenge here, you'll need to apply your own unique creativity to the problem 😄.
 
 The next chapter will help you handle a common challenge when working with user supplied data: you need to dynamically adapt the user interface to better fit the data.
 I'll start with some simple techniques that are easy to understand and can be applied in many situations, gradually working our way up to fully a dynamic user-interface generated by code.