Add Area and Centroid nodes (#1749)

* initial attempt for area node

* allow node preview for more types

* make AreaNode sync and add CentroidNode

* cargo fmt

* preview of DVec2

* make the nodes async again

* use segment domain instead of region domain

* modify the check for linearity

* create a limit for area in centroid calculation

* cargo fmt

* reverse unnecessary changes

* add threshold to area calculation too.

* handle zero area edge case

* add todo comment

* implement 1D centroid and use it as fallback

* formatting floats to skip last zero

* add Centroid Type radio button to Centroid Node

* rename docs to use area and perimeter centroid

* add web demos for perimeter centroid

* add tests for perimeter centroid

* add fallback to use average of points

* Fix for broken area

* missing fixes

* Code review and rename Perimeter Centroid to Length Centroid

* Use dummy footprint in Area and Centroid nodes

* add doc and todo to clarify when `is_linear` fails

* use epsilon instead of zero

---------

Co-authored-by: 0hypercube <0hypercube@gmail.com>
Co-authored-by: Keavon Chambers <keavon@keavon.com>
Co-authored-by: Dennis Kobert <dennis@kobert.dev>

website/other/bezier-rs-demos/wasm/src/bezier.rs

@@ -148,6 +148,13 @@ impl WasmBezier {
 		wrap_svg_tag(format!("{bezier}{}", draw_text(format!("Length: {:.2}", self.0.length(None)), TEXT_OFFSET_X, TEXT_OFFSET_Y, BLACK)))
 	}
 
+	pub fn length_centroid(&self) -> String {
+		let bezier = self.get_bezier_path();
+		let centroid = self.0.length_centroid(None);
+		let point_text = draw_circle(centroid, 4., RED, 1.5, WHITE);
+		wrap_svg_tag(format!("{bezier}{}", point_text))
+	}
+
 	pub fn evaluate(&self, raw_t: f64, t_variant: String) -> String {
 		let bezier = self.get_bezier_path();
 		let t = parse_t_variant(&t_variant, raw_t);