[pathkit] Add .ready() to initialize

See https://github.com/kripken/emscripten/issues/5820 and
https://skia-review.googlesource.com/c/skia/+/181177 for more context.

(Problem was discovered in CanvasKit, and this ports the same fix to
PathKit).

Bug: skia:
Change-Id: Ic8b2fb399210631a571595a5b3d11d1736c00def
Reviewed-on: https://skia-review.googlesource.com/c/181178
Reviewed-by: Joe Gregorio <jcgregorio@google.com>
diff --git a/modules/pathkit/npm-wasm/example.html b/modules/pathkit/npm-wasm/example.html
index 488f6ec..d7c2469 100644
--- a/modules/pathkit/npm-wasm/example.html
+++ b/modules/pathkit/npm-wasm/example.html
@@ -53,7 +53,7 @@
 
   PathKitInit({
     locateFile: (file) => '/node_modules/pathkit-wasm/bin/'+file,
-  }).then((PathKit) => {
+  }).ready().then((PathKit) => {
     window.PathKit = PathKit;
     OutputsExample(PathKit);
     Path2DExample(PathKit);