Fix live waveform scaling, drop GTK deps, and document the project

- Tune the live spectrum display to a fixed range matched to real per-FFT-bin
  levels (-40..0 dB) so typical content sits mid-screen instead of flying to
  the top or hugging the bottom; widen the SENS offset control to -48..+24 dB
- Disable JUCE_WEB_BROWSER so the WebKitGTK WebBrowserComponent (unused) is
  compiled out, letting the plugin build on Artix/Arch without GTK/WebKit dev
  headers
- Add a verbose README covering the bands, parameters, controls, structure,
  DSP, build steps, and the Linux/Artix note

Source/PluginEditor.h

@@ -35,7 +35,7 @@ public:
     float saturation = 1.0f;
     float brightness = 1.0f;
     float waveformOpacity = 0.2f;
-    float waveSensitivity = 0.0f; // in dB, added to the spectrum display level
+    float waveSensitivity = 0.0f; // in dB, vertical offset added to the live waveform trace
     float uiScale = 1.0f;
 
 private: