Playground doesn't support effects

[johnridesabike]

Trying to use effects returns this error:

Error: Reference to undefined global `Stdlib__Effect'

Reproduction: https://ocaml.org/play#code=b3BlbiBFZmZlY3QKb3BlbiBFZmZlY3QuRGVlcApsZXQgaW52ZXJ0ICh0eXBlIGEpIH4oaXRlciA6IChhIC0%2BIHVuaXQpIC0%2BIHVuaXQpIDogYSBTZXEudCA9CiAgbGV0IG1vZHVsZSBNID0gc3RydWN0CiAgICB0eXBlIF8gRWZmZWN0LnQgKz0gWWllbGQgOiBhIC0%2BIHVuaXQgdAogIGVuZCBpbgogIGxldCB5aWVsZCB2ID0gcGVyZm9ybSAoTS5ZaWVsZCB2KSBpbgogIGZ1biAoKSAtPiBtYXRjaF93aXRoIGl0ZXIgeWllbGQKICB7IHJldGMgPSAoZnVuIF8gLT4gU2VxLk5pbCk7CiAgICBleG5jID0gcmFpc2U7CiAgICBlZmZjID0gZnVuICh0eXBlIGIpIChlZmYgOiBiIEVmZmVjdC50KSAtPgogICAgICBtYXRjaCBlZmYgd2l0aAogICAgICB8IE0uWWllbGQgdiAtPiBTb21lIChmdW4gKGs6IChiLF8pIGNvbnRpbnVhdGlvbikgLT4KICAgICAgICAgIFNlcS5Db25zICh2LCBjb250aW51ZSBrKSkKICAgICAgfCBfIC0%2BIE5vbmUgfQ%3D%3D