add short link and text about docker

Author: gregor-j

docker.md

@@ -0,0 +1,13 @@
+# Docker images with SAP modules
+
+> The SAP NetWeaver RFC SDK 7.50 is not provided under an open source
+> license at the current time. Consequently, the files provided through this SDK
+> are only for use by licensed customers and should not be redistributed as part
+> of an open source project.
+
+E-Mail from _opensource@sap.com_, Feb. 2020
+
+You will have to [build the docker image containing a SAP module][docker]
+yourself.
+
+[docker]: https://github.com/php-sap/docker-kralik "PHP 7 docker image for Gregor Kraliks SAPNWRFC module"

index.md

@@ -74,6 +74,7 @@ Too short? Confused? You should probably read the documentation. 😉
     - [Configure a connection](saprfc-config)
     - [Configure the SAP remote function call](saprfc-function)
 * [DateTime conversions for SAP](datetime)
+* [Docker images with SAP modules](docker)
 
 [koucky]: http://saprfc.sourceforge.net/ "SAPRFC extension module for PHP"
 [harding]: https://github.com/piersharding/php-sapnwrfc "SAP RFC Connector using the SAP NW RFC SDK for PHP"