Added shaders

Shaders/ursc/canvas_item/dithering.gdshader

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+#pragma disable_preprocessor
+
+shader_type canvas_item;
+
+// 0: bypass
+uniform float color_depth: hint_range(0, 32, 8) = 24;
+
+uniform sampler2D dithering_pattern_texture:
+	hint_default_white, repeat_enable, filter_nearest;
+
+void fragment()
+{
+	vec3 base_color = texture(TEXTURE, UV).rgb;
+
+	if (color_depth > 0.0)
+	{
+		vec2 dpt_size = vec2(textureSize(dithering_pattern_texture, 0));
+		vec2 texture_size = vec2(textureSize(TEXTURE, 0));
+
+		vec3 dithering = texture(
+			dithering_pattern_texture, UV * (texture_size / dpt_size)).rgb - 0.5;
+
+		COLOR.rgb = round(
+			base_color.rgb * color_depth + dithering) / color_depth;
+	}
+	else
+	{
+		COLOR.rgb = base_color;
+	}
+}

Shaders/ursc/canvas_item/dithering.gdshader.uid

@@ -0,0 +1 @@
+uid://di7y6sooqe3t4

Shaders/ursc/canvas_item/fade.gdshader

@@ -0,0 +1,16 @@
+#pragma disable_preprocessor
+
+shader_type canvas_item;
+
+uniform sampler2D SCREEN_TEXTURE: hint_screen_texture, filter_nearest, repeat_disable;
+
+//  1: white
+// -1: black
+uniform int mode: hint_range(-1, 1, 2) = -1;
+
+void fragment()
+{
+	vec3 screen_color = texture(SCREEN_TEXTURE, SCREEN_UV).rgb;
+	COLOR.rgb = screen_color + COLOR.a * float(mode);
+	COLOR.a = 1.0;
+}

Shaders/ursc/canvas_item/fade.gdshader.uid

@@ -0,0 +1 @@
+uid://ddas7a15ugrdn