Update README.md

Author: andrei-m-code

README.md

@@ -113,7 +113,7 @@ Use `[JsonProperty("alert-type")]` attribute to serialize C# properties into JSO
 
 # Known Issues
 
-* Doesn't seem like it's running on Mono [#55](https://github.com/andrei-m-code/net-core-push-notifications/issues/55)
+* Doesn't seem like it's running on Mono [#55](https://github.com/andrei-m-code/net-core-push-notifications/issues/55).
 
 # MIT License