Update README.md

typo fix in nuget command: pacakage to package

Author: josemrosilva

README.md

@@ -87,7 +87,7 @@ project. It provides a dynamic, but more succinct API than the above options.
 
 ## Install ServiceStack.Text
 
-    PM> Install-Pacakage ServiceStack.Text
+    PM> Install-Package ServiceStack.Text
 
 _Commercial support will be available for ServiceStack, contact [email protected] for details_