fix typo

Author: m1rm

README.md

@@ -19,7 +19,7 @@ the Arch Linux package statistics website.
 ## Dev Mode
 Run `just dev` to watch for template and Go changes and rebuild automatically (requires [air](https://github.com/air-verse/air)).
 The automatic rebuild does not include assets (images, JS, CSS) and all unused classes are stripped during the build process.
-Thus, ehen changing classes for example, you might need to stop the dev server and run `just build-assets` and then start
+Thus, when changing classes for example, you might need to stop the dev server and run `just build-assets` and then start
 the project again.
 
 ## Tests