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)*

editor/src/tool/tools/eyedropper.rs

@@ -0,0 +1,39 @@
+use crate::consts::SELECTION_TOLERANCE;
+use crate::message_prelude::*;
+use crate::tool::{ToolActionHandlerData, ToolMessage};
+use glam::DVec2;
+use graphene::layers::LayerDataType;
+use graphene::Quad;
+
+#[derive(Default)]
+pub struct Eyedropper;
+
+#[impl_message(Message, ToolMessage, Eyedropper)]
+#[derive(PartialEq, Clone, Debug, Hash)]
+pub enum EyedropperMessage {
+	LeftMouseDown,
+	RightMouseDown,
+}
+
+impl<'a> MessageHandler<ToolMessage, ToolActionHandlerData<'a>> for Eyedropper {
+	fn process_action(&mut self, action: ToolMessage, data: ToolActionHandlerData<'a>, responses: &mut VecDeque<Message>) {
+		let mouse_pos = data.2.mouse.position;
+		let tolerance = DVec2::splat(SELECTION_TOLERANCE);
+		let quad = Quad::from_box([mouse_pos.as_f64() - tolerance, mouse_pos.as_f64() + tolerance]);
+
+		if let Some(path) = data.0.document.intersects_quad_root(quad).last() {
+			if let Ok(layer) = data.0.document.layer(path) {
+				if let LayerDataType::Shape(s) = &layer.data {
+					s.style.fill().and_then(|fill| {
+						fill.color().map(|color| match action {
+							ToolMessage::Eyedropper(EyedropperMessage::LeftMouseDown) => responses.push_back(ToolMessage::SelectPrimaryColor(color).into()),
+							ToolMessage::Eyedropper(EyedropperMessage::RightMouseDown) => responses.push_back(ToolMessage::SelectSecondaryColor(color).into()),
+							_ => {}
+						})
+					});
+				}
+			}
+		}
+	}
+	advertise_actions!(EyedropperMessageDiscriminant; LeftMouseDown, RightMouseDown);
+}