Add FFT Visualizer Demo

[wyhinton]

It'd be great if the repo included a simple eq visualizer demo that clearly demonstrates how to use the new fft input.

I imagine it could look like this (maybe even simpler).

[wyhinton]

Bumping this, or does anyone know of any examples that show how to use the fft input uniform?

[wyhinton]

Could you tell me why this doesn't work?
@jorisdejong could you tell me why this shader doesn't work?

Isn't the FFT Param provided as a uniform array of float values?

#include "FFT_BASIC.h"
static PluginInstance p = Source::CreatePlugin< FFT_BASIC >({"FFT_BASIC","FFT_BASIC"});

static const std::string fshader = R"(
precision mediump float; 


void main()
{
    float t = TEST[1000];
    gl_FragColor = vec4(t);
}
)";

FFT_BASIC::FFT_BASIC()
{
SetFragmentShader(fshader);
AddParam(ParamFFT::Create("TEST"));


}

FFT_BASIC::~FFT_BASIC()
{
}