Add link to Fake SFTP Server Lambda

People should be aware of the alternative becaue they cannot use the
rule with JUnit Jupiter and TestNG.

Author: stefanbirkner

README.md

@@ -15,6 +15,9 @@ if you want to use it with an older version of Java.
 I want to thank my former team SAM at ThoughtWorks for using this library and
 @crizzis, @OArtyomov and @TheSentinel454 for their feature requests.
 
+There is an alternative to Fake SFTP Server Rule that is independent of the
+test framework. Its name is
+[Fake SFTP Server Lambda](https://github.com/stefanbirkner/fake-sftp-server-lambda).
 
 ## Installation
 

pom.xml

@@ -9,7 +9,7 @@
     </parent>
 
     <artifactId>fake-sftp-server-rule</artifactId>
-    <version>2.0.1</version>
+    <version>2.1.0-SNAPSHOT</version>
     <packaging>jar</packaging>
 
     <name>Fake SFTP Server Rule</name>