feat: include for glsl (#24)

* refactor(gameplay): remove unused includes and members, clear vertex data after upload

* feat(shader-tools): add recursive #include support for shader sources

* refactor(shaders): extract noise and sky color functions into shared GLSL includes

assets/shaders/noise.glsl

@@ -0,0 +1,25 @@
+float hash(vec2 p) {
+    return fract(sin(dot(p, vec2(127.1, 311.7))) * 43758.5453123);
+}
+
+float noise(vec2 p) {
+    vec2 i = floor(p);
+    vec2 f = fract(p);
+    f = f * f * (3.0 - 2.0 * f);
+    float a = hash(i);
+    float b = hash(i + vec2(1.0, 0.0));
+    float c = hash(i + vec2(0.0, 1.0));
+    float d = hash(i + vec2(1.0, 1.0));
+    return mix(mix(a, b, f.x), mix(c, d, f.x), f.y);
+}
+
+float fbm(vec2 p) {
+    float v = 0.0;
+    float amp = 0.5;
+    for (int i = 0; i < 5; i++) {
+        v += amp * noise(p);
+        p *= 2.0;
+        amp *= 0.5;
+    }
+    return v;
+}