Add link to README.

Author: Crell

README.md

@@ -1,6 +1,6 @@
 # Symfony Flex bridge for Platform.sh
 
-This simple bridge library connects a Symfony Flex-based application to Platform.sh.  In the typical case it should be completely fire-and-forget.
+This simple bridge library connects a Symfony Flex-based application to [Platform.sh](https://platform.sh/).  In the typical case it should be completely fire-and-forget.
 
 Symfony Flex expects all configuration to come in through environment variables with specific names in a specific format.  Platform.sh provides configuration information as environment variables in a different specific format.  This library handles mapping the Platform.sh variables to the format Symfony Flex expects for common values.