feat: add eraser tool trail (#7511)

Co-authored-by: dwelle <5153846+dwelle@users.noreply.github.com>

packages/excalidraw/utils.ts

@@ -1013,6 +1013,40 @@ export function addEventListener(
   };
 }
 
+const average = (a: number, b: number) => (a + b) / 2;
+export function getSvgPathFromStroke(points: number[][], closed = true) {
+  const len = points.length;
+
+  if (len < 4) {
+    return ``;
+  }
+
+  let a = points[0];
+  let b = points[1];
+  const c = points[2];
+
+  let result = `M${a[0].toFixed(2)},${a[1].toFixed(2)} Q${b[0].toFixed(
+    2,
+  )},${b[1].toFixed(2)} ${average(b[0], c[0]).toFixed(2)},${average(
+    b[1],
+    c[1],
+  ).toFixed(2)} T`;
+
+  for (let i = 2, max = len - 1; i < max; i++) {
+    a = points[i];
+    b = points[i + 1];
+    result += `${average(a[0], b[0]).toFixed(2)},${average(a[1], b[1]).toFixed(
+      2,
+    )} `;
+  }
+
+  if (closed) {
+    result += "Z";
+  }
+
+  return result;
+}
+
 export const normalizeEOL = (str: string) => {
   return str.replace(/\r?\n|\r/g, "\n");
 };