Added description of the Cascade Validation plugin

Author: dauer

grails-plugins/io/github/gpc/cascade-validation.yml

@@ -1,5 +1,6 @@
 name: cascade-validation
-desc: Grails Cascade Validation plugin
+desc: This plugin establishes a cascade constraint property for validatable objects, that being domain objects,
+  and objects implementing grails.validation.Validateable
 coords: io.github.gpc:cascade-validation
 owner: gpc
 vcs: https://github.com/gpc/grails-cascade-validation