Add SDL2 example with custom colorbuffer and font rendering

[lzzrhx]

This example includes a custom colorbuffer array, some basic functions for drawing to the colorbuffer and functions for font rendering (the font is rendered to a separate colorbuffer, as this allows for only clearing the sections of the buffer that's been drawn to, and thus gives much better performance (since clearing the entire colorbuffer each frame can be quite slow)). The bits for the included font are based on ToshibaSat 8x16. I am not very familiar with how to include licenses properly, but gave it a go in the included LICENSE file.

As an example a procedural Odin logo is drawn to the main colorbuffer.

I've used this setup in two projects:

• voxel-space-cpu
• ray-tracer-cpu

Checklist before submitting:

• This example has been added to .github/workflows/check.yml (for automatic testing)
• This example compiles cleanly with flags -vet -strict-style -vet-tabs -disallow-do -warnings-as-errors
• This example the naming and style convention: https://github.com/odin-lang/examples/wiki/Naming-and-style-convention (exceptions can be made for ports of examples that need to match 1:1 to the original source).
• By submitting, I understand that this example is made available under these licenses: Public Domain and Odin's zlib license. Only for third-party dependencies are other licenses allowed.