Add Shape Tool for drawing polygons (#75)

* ⬠ Add polygon drawing tool

* 🔤 Minor fix of variable and function names

* ❌ Remove stroke

* ⌨️ Use N key as polygo tool shortcut.

* ⌨️ Now using key Y for polygons.

* ⌨️ The tooltip for the shortcut is fixed

core/document/src/operation.rs

@@ -24,6 +24,15 @@ pub enum Operation {
 		x1: f64,
 		y1: f64,
 	},
+	AddShape {
+		path: Vec<LayerId>,
+		insert_index: isize,
+		x0: f64,
+		y0: f64,
+		x1: f64,
+		y1: f64,
+		sides: u8,
+	},
 	DeleteLayer {
 		path: Vec<LayerId>,
 	},