feat: add triangle arrowhead (#4024)

Co-authored-by: ad1992 <aakansha1216@gmail.com>
Co-authored-by: dwelle <luzar.david@gmail.com>

src/element/bounds.ts

@@ -258,6 +258,7 @@ export const getArrowheadPoints = (
     arrow: 30,
     bar: 15,
     dot: 15,
+    triangle: 15,
   }[arrowhead]; // pixels (will differ for each arrowhead)
 
   let length = 0;
@@ -294,6 +295,7 @@ export const getArrowheadPoints = (
   const angle = {
     arrow: 20,
     bar: 90,
+    triangle: 25,
   }[arrowhead]; // degrees
 
   // Return points

src/element/types.ts

@@ -129,7 +129,7 @@ export type PointBinding = {
   gap: number;
 };
 
-export type Arrowhead = "arrow" | "bar" | "dot";
+export type Arrowhead = "arrow" | "bar" | "dot" | "triangle";
 
 export type ExcalidrawLinearElement = _ExcalidrawElementBase &
   Readonly<{