TUIC todo

TUIC TASKS

new error TUI_ERROR_INSTANCE_DAMAGED
new error TUI_ERROR_INVALID_COLOR_COUNT
new error TUI_ERROR_NULL_COLORS
new error TUI_ERROR_INVALID_IMAGE_CHANNEL_COUNT
document all places where TUI_ERROR_BACKEND_SPECIFIC can be thrown
release 1.2

for 1.3:
panel masked rendering for rendering regions within a TuiPanel
TuiTexture object for rendering background images
TuiFont object for loading glyphs from TTF font files (using stb_truetype)
TuiAtlasBuilder object for dynamic TuiGlyphAtlas construction
blend flags and remake existing blend modes to use the flags
sdf, mtsdf msdf etc blend modes
remake the examples
CMake options to disable string consts and conversion functions to decrease executable size

for 2.0:
input/windowing system interface
add sdl2 to opengl33 backend using input interface

for 2.1:
TUI_LAYOUT_FLAG_SPRITE (simillar to RLTK/Bracket Lib fancy renderer)
add curses backend
add CMake option to use lib_png instead of stb_image and freetype instead of stb_truetype

for 2.2:
add Vulkan/SDL2 backend