Add checks

[Brian-ED]

raylib has some checking functions inbuilt, like isFontReady, IsImage, IsTexture, etc. Using these and maybe some extra we could validate a lot of function's inputs "properly".

Though the raylib validity functions are honestly not great, they just check if pointers are null and size is over 0 and such... but size of images can very well be 0, why would that be invalid? probably need to reimplement some of the checks.

[Brian-ED]

raylib.isAudioDeviceReady can also be implemented for _withAudio after init-ing audio device

[Brian-ED]

(And isWaveReady, isSoundReady, isMusicReady, isAudioStreamReady, isShaderReady, isTextureReady, isRenderTextureReady, isModelReady, isMaterialReady)