feat(art): add storybook meadow and woodland villagers

world/presentation/materials/storybook_surface.gdshader

@@ -0,0 +1,24 @@
+shader_type spatial;
+render_mode specular_disabled;
+uniform vec3 albedo : source_color = vec3(0.8, 0.72, 0.52);
+uniform float paint_strength : hint_range(0.0, 0.2) = 0.04;
+varying vec3 paint_position;
+
+void vertex() {
+	paint_position = (MODEL_MATRIX * vec4(VERTEX, 1.0)).xyz;
+}
+
+void fragment() {
+	float brush = sin(paint_position.x * 2.1 + sin(paint_position.y * 3.0)) * sin(paint_position.z * 2.8 + paint_position.y);
+	ALBEDO = albedo * (1.0 + brush * paint_strength);
+	ROUGHNESS = 1.0;
+}
+
+void light() {
+	float ndl = dot(NORMAL, LIGHT);
+	float middle = smoothstep(-0.10, 0.03, ndl);
+	float sunny = smoothstep(0.48, 0.58, ndl);
+	vec3 shade = mix(vec3(0.26, 0.34, 0.40), vec3(0.74), middle);
+	shade = mix(shade, vec3(1.0, 0.97, 0.88), sunny);
+	DIFFUSE_LIGHT += shade * ATTENUATION * LIGHT_COLOR / PI;
+}