Adding contribution details.

Grabbed from former OSGeo trac: https://trac.osgeo.org/qgis/

Author: gacarrillor

doc/contributors.json

@@ -425,6 +425,8 @@
       "properties": {
         "Name": "Germán Carrillo",
         "Committer": "No",
+        "First Commit Message": "Applied patch to fix legend cursor. Provided by gcarrillo",
+        "First Commit Date": "10-06-2009",
         "GIT Nickname": "gacarrillor"
       },
       "geometry": {