check in font-atlas-sdf in dependencies

- used in 'fancy' scattergl traces
- control its version here, instead of it being a 3rd-party dep

Author: etpinard

package.json

@@ -64,6 +64,7 @@
     "delaunay-triangulate": "^1.1.6",
     "es6-promise": "^3.0.2",
     "fast-isnumeric": "^1.1.1",
+    "font-atlas-sdf": "^1.3.3",
     "gl-contour2d": "^1.1.2",
     "gl-error2d": "^1.2.1",
     "gl-error3d": "^1.0.6",