Now that the custom dictionary can be built from topics with specific extended properties assigned to them, and that these topics are now used in the DocBuilder spell checker, the XML editor needs to be updated to provide a similar experience.

1. Right clicking on words or phrases found in the custom dictionary needs to open the relevant custom dictionary topic.
2. Valid words need to come from the standard dictionary as well as the custom dictionary topics.
3. Provide the ability to add words to the custom dictionary from the XML editor.