refactor: make the whole thing more generic

modules/home-manager/desktops/hyprland/hypr/shaders/extradark.frag

@@ -0,0 +1,21 @@
+// vim: set ft=glsl:
+// blue light filter shader
+// values from https://reshade.me/forum/shader-discussion/3673-blue-light-filter-similar-to-f-lux
+
+precision mediump float;
+varying vec2 v_texcoord;
+uniform sampler2D tex;
+
+void main() {
+
+    vec4 pixColor = texture2D(tex, v_texcoord);
+
+    // red
+    pixColor[0] *= 0.7;
+    // green
+    pixColor[1] *= 0.6;
+    // blue
+    pixColor[2] *= 0.5;
+
+    gl_FragColor = pixColor;
+}