bump point-cluster to 2.1.1

- which is transpiled to ES5

Author: etpinard

package-lock.json

@@ -95,7 +95,7 @@
     "ndarray-fill": "^1.0.2",
     "ndarray-homography": "^1.0.0",
     "ndarray-ops": "^1.2.2",
-    "point-cluster": "^2.0.0",
+    "point-cluster": "^2.1.1",
     "polybooljs": "^1.2.0",
     "regl": "^1.3.1",
     "regl-error2d": "^2.0.3",