Added two missing guidelines

Author: egonw

index.md

@@ -36,6 +36,8 @@ layout: page
 
 * [Installing Open PHACTS (needs review/update)](http://github.com/openphacts/ops-docker/blob/master/README.md)
 * [Loading additional data](/Loading-additional-data)
+* [Guidelines for exposing data as RDF in Open PHACTS](https://openphacts.github.io/Documentation/rdfguide/)
+* [Encoding units and unit types in RDF using QUDT](https://openphacts.github.io/Documentation/units/)
 
 ## Projects with documentation: