Easing Into It: The anim module (#2799)

* new anim folder, new easings

* deprecate easing.py by deleting it

it doesn't look like it's used anywhere internally

* explain constants

* remove obsolete examples

* Get doc building

* minor improvements

* just define the methods on the class

* Fix sphinx conf to render docstrings

* Fix inclusion of items in doc

* Fix doc build after adding to the quickindex file.

* Convert EasingFunction into a typing.Protocol so it gets picked up by doc build + explain why

* Correct Sphinx style issues and broken cross-references

* Explain how of pyglet.math Matrix types won't work with easing (matmul)

* Add an __all__ to arcade.anim.easing

* ./make.py format

* Remove unused typing.Callable import

* Another ruff formatter run

* Rename perc to norm as discussed

* Rename `Animatable` to `Interpolatable`, as per @pushfoo

---------

Co-authored-by: pushfoo <[email protected]>

Author: DigiDuncan

arcade/anim/__init__.py

@@ -0,0 +1,3 @@
+from arcade.anim.easing import ease, Easing, lerp, norm
+
+__all__ = ["ease", "Easing", "lerp", "norm"]