fix: Use the returned, sorted list of children

feature: Reorder elements of a layers with :sort-with

feature: A new element for printing text

feature: Add a new animation called goto

feature: An a new element to display an image

fix: Revert the resource-key function, fix setf get-child

feature: Basic display of a tiled map

fix: The first to be add is the first to be drawn

chore: Add a LICENSE and a README

feature: It is now possible to add animation (at least to tiles)

refactor: width and height becomes true generic method

feature: Introduce  fairy/tiled to work with the famous game editor

feature: Specify a keys equality when deleting a child (optional)

feature: Retrieve a child from a layer with its key

feature: Add a new attribute to hide an element

feature: It is possible to associate a key to an element in a layer

refactor: Use classes in place of structs

refactor: A more lispy implementation

doc: Add a new example file

feature: Add a proper root element