[gxml] Documenting GXml.Error codes

[Daniel Espinosa Ortiz <despinosa src gnome org>]

commit 6231b785a48aa7571b7994facb8a68df0ef6c985
Author: Daniel Espinosa <esodan gmail com>
Date:   Thu May 11 12:34:51 2017 -0500

    Documenting GXml.Error codes

 gxml/GXmlNode.vala |    4 +++-
 1 files changed, 3 insertions(+), 1 deletions(-)
---
diff --git a/gxml/GXmlNode.vala b/gxml/GXmlNode.vala
index da5623a..7056849 100644
--- a/gxml/GXmlNode.vala
+++ b/gxml/GXmlNode.vala
@@ -21,7 +21,9 @@
  */
 
 using Gee;
-
+/**
+ * Auxiliary error codes for parsing/writting libxml2 powered classes
+ */
 public errordomain GXml.Error {
                NOT_SUPPORTED, /* TODO: GET RID OF THIS */
                PARSER, WRITER;