Add a reusable check for WASM platfoms

Author: agriyakhetarpal

zarr/tests/util.py

@@ -1,5 +1,7 @@
 import collections
 import os
+import sys
+import platform
 import tempfile
 from typing import Any, Mapping, Sequence
 from zarr.context import Context
@@ -118,3 +120,7 @@ def mktemp(**kwargs):
     f = tempfile.NamedTemporaryFile(**kwargs)
     f.close()
     return f.name
+
+
+def is_wasm():
+    return (sys.platform == "emscripten" or platform.machine() in ["wasm32", "wasm64"])