Update README.md

Author: daenuprobst

README.md

@@ -29,6 +29,10 @@ Current Version: **2.1.2**
 
 If you use this code or application, please cite the original paper published by the Journal of Chemical Information and Modeling: [10.1021/acs.jcim.7b00425](http://dx.doi.org/10.1021/acs.jcim.7b00425)
 
+## Legacy Documentation
+
+As of now, there is full backwards compatibility.
+
 ### Examples
 
 An example using the light theme can be found [here](http://doc.gdb.tools/smilesDrawer/sd/example/index_light.html), while one using the dark theme can be found [here](http://doc.gdb.tools/smilesDrawer/sd/example/index.html) . The colors of SmilesDrawer are completely configurable.