Safari 14.6+ - suspend is not working

[RayJi0428]

In the _autoSuspend function, self.ctx.suspend().then(... won't fire at iOS Safari 14.6+.

so that if no sound played after 30 seconds, self.state will not change to 'suspended', it'll stay at 'suspending',

[keiththomas1]

I have a possible fix for this here: #1660