Added audio examples. Fix bug in raylib textFormat.

[ramonmeza]

Implemented raylib's (audio mixed processor example)[https://github.com/raysan5/raylib/blob/master/examples/audio/audio_mixed_processor.c].

I copied the audio files from raylib's repository and added them to this one under resources. Whenever someone gets around to implementing zig build examples, they will need to include that resources directory with the executable for this example to work properly.

Below is an image of the results of running zig build mixed_processor

[ramonmeza]

I compared to the original example. I have much more distortion. I will iron out these issues.

[ramonmeza]

I figured out there was a bug in raylib.zig. textFormat was switching on .Struct, which was throwing an error. I looked at some of the innards and found @"struct" is an alias for Struct, so I switched on that instead.

[ramonmeza]

All of the audio examples have been added. Here's the list

zig build mixed_processor
zig build module_playing
zig build music_stream
zig build raw_stream
zig build sound_loading
zig build sound_multi
zig build stream_effects

The only issues I notice:

• Allocation in stream_effects should instead pass the allocator as a parameter rather than hardcoding it in.
• stream_effects seems to be slightly distorted when using LPF filter compared to native C build. Not sure why that is.

[Not-Nik]

This should be two PRs. One for the fix, one for the examples. Also take some time to read through CONTRIBUTING.md.

zig build examples is implemented, so any build steps should work with this PR (should as in, you should make them work if they don't).