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/fill.rs

@@ -0,0 +1,33 @@
+use crate::consts::SELECTION_TOLERANCE;
+use crate::message_prelude::*;
+use crate::tool::ToolActionHandlerData;
+use glam::DVec2;
+use graphene::{Operation, Quad};
+
+#[derive(Default)]
+pub struct Fill;
+
+#[impl_message(Message, ToolMessage, Fill)]
+#[derive(PartialEq, Clone, Debug, Hash)]
+pub enum FillMessage {
+	MouseDown,
+}
+
+impl<'a> MessageHandler<ToolMessage, ToolActionHandlerData<'a>> for Fill {
+	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() {
+			responses.push_back(
+				Operation::FillLayer {
+					path: path.to_vec(),
+					color: data.1.primary_color,
+				}
+				.into(),
+			);
+		}
+	}
+	advertise_actions!(FillMessageDiscriminant; MouseDown);
+}