Update README.md

Author: freekmurze

README.md

@@ -37,7 +37,7 @@ We invest a lot of resources into creating [best in class open source packages](
 
 We highly appreciate you sending us a postcard from your hometown, mentioning which of our package(s) you are using. You'll find our address on [our contact page](https://spatie.be/about-us). We publish all received postcards on [our virtual postcard wall](https://spatie.be/open-source/postcards).
 
-We understand if you don't send us a postcard for this particular package
+We understand if you don't send us a postcard for this particular package.
 
 ## Changelog