Text input widgets no longer use terminal cursor.

Text input widgets no longer use terminal cursor. Instead they draw a "virtual cursor".

Structured canvas arrays.

Before, TextWidget canvas arrays had dtype object. Now canvas arrays have dtype ("char", "U1"), ("bold", "?"), ("italic", "?"), ("underline", "?"), ("strikethrough", "?").

Additional changes:

• add_text method of TextWidget is now add_str and add_text is now a function that adds multiline text to arbitrary views of a canvas array.
• Color theming is completely revamped.
• CanvasView removed.
• Animated toggle buttons added.

TextPanel added.

TextPanel added for multiline static text.

Added `invert` arg to `BrailleVideoPlayer` and `root_dir` property to `FileChooser`.

Added invert argument to BrailleVideoPlayer and root_dir property to FileChooser.

BrailleVideoPlayer added. Fixed several input handling bugs.

BrailleVideoPlayer widget plays videos in mono-chrome or optional grayscale with braille unicode characters.

Bug Fixes

Sporadic mouse input on Windows could break the mouse input handler. It's now robust against this.
Terminal resize events on Linux were cleared before being processed. Oops.
Backspace ansi wasn't correctly mapped on WSL.

Bug Fix: Text input widgets no longer focus on add.

Focusing on add prevents other focusables from being added to __focus_widgets when they are being added to the tree simultaneously.

`Sprite` class removed. Split widgets' names swapped.

Sprite helper class removed. This class was made to help with reading, resizing, and compositing textures. Three
functions have been added: read_texture, resize_texture, and composite to replace Sprite.

RaySprites from the raycaster module have now reclaimed their original name, Sprite.

Horizontal and vertical split layout widgets had their names swapped. This is now fixed. Also, HSplitLayout's handle is thinned to match VSplitLayout's handle.

`reversed` method added to `ColorPair`. Animation bug fix.

ColorPair.reversed() returns a new ColorPair with the foreground and background colors reversed.

Animation no longer skips last frame.

Text input widgets added.

Two text input widgets added: TextPad for multi-line editable text and Textbox for single-line editable text.

Remove setup.py and setup.cfg and instead use pyproject.toml.