I don't think you'd want that website. Whisper is fairly efficient (even an old GTX can do pretty well at 4x-8x real-time speed), but a website like that would still require pretty expensive cloud GPUs. It's really not possible to imagine that a website like that would not be data mining you and selling all your audio to advertisers to pay off investors.

Better to buy a GPU and do it yourself. (Good news: it takes like 30 seconds to install)