docs: added initial docs about configuration.
docs: added initial docs about configuration.

Related to #63.

gleez/gandalf,flaviamissi/gandalf,gleez/gandalf,scorphus/gandalf,marcelometal/gandalf,tsuru/gandalf,scorphus/gandalf,tsuru/gandalf,marcelometal/gandalf,flaviamissi/gandalf,marcelometal/gandalf,gleez/gandalf