feat: add option for custom "not found message"

[patou]

Fix #282 Display not found message

The properties notFoundMessage isn't used in the lib. If there are 0 result and the notFountMessage is setted, display the message :

In the resultList class, classNames isn't filled. Add two new properties in the classNames config :

• resultlist : class for style the result list
• item : class for style items in the result list
• notfound : class for style when no results (by default use italic tests)

By default, the config option notFoundMessage as the default unused value : 'Sorry, that address could not be found.', Does change it to default to empty, to keep the same behavior as now ?

[patou]

Is there any think I can do for the PR merged ?

[smeijer]

Sorry, I should have responded earlier. Can you change the default behavior to be the current situation? Even though I believe your default is better, I don't want to change the behavior for existing implementations.

[patou]

@smeijer I change to use not display not found message by default.