Restructure project directories (#333)

`/client/web` -> `/frontend`
`/client/cli` -> *delete for now*
`/client/native` -> *delete for now*
`/core/editor` -> `/editor`
`/core/document` -> `/graphene`
`/core/renderer` -> `/charcoal`
`/core/proc-macro` -> `/proc-macros` *(now plural)*

graphene/src/layers/blend_mode.rs

@@ -0,0 +1,44 @@
+use serde::{Deserialize, Serialize};
+
+#[derive(PartialEq, Copy, Clone, Debug, Serialize, Deserialize)]
+pub enum BlendMode {
+	Normal,
+	Multiply,
+	Darken,
+	ColorBurn,
+	Screen,
+	Lighten,
+	ColorDodge,
+	Overlay,
+	SoftLight,
+	HardLight,
+	Difference,
+	Exclusion,
+	Hue,
+	Saturation,
+	Color,
+	Luminosity,
+}
+
+impl BlendMode {
+	pub fn to_svg_style_name(&self) -> &str {
+		match self {
+			BlendMode::Normal => "normal",
+			BlendMode::Multiply => "multiply",
+			BlendMode::Darken => "darken",
+			BlendMode::ColorBurn => "color-burn",
+			BlendMode::Screen => "screen",
+			BlendMode::Lighten => "lighten",
+			BlendMode::ColorDodge => "color-dodge",
+			BlendMode::Overlay => "overlay",
+			BlendMode::SoftLight => "soft-light",
+			BlendMode::HardLight => "hard-light",
+			BlendMode::Difference => "difference",
+			BlendMode::Exclusion => "exclusion",
+			BlendMode::Hue => "hue",
+			BlendMode::Saturation => "saturation",
+			BlendMode::Color => "color",
+			BlendMode::Luminosity => "luminosity",
+		}
+	}
+}