Fix qualityArgument in toBlob example
Fix qualityArgument in toBlob example

The [qualityArgument](https://developer.mozilla.org/en-US/docs/Web/API/HTMLCanvasElement/toBlob) is supposed to be a value between 0 and 1. The ReadMe was confusing since it specifies `90` but its value is passed directly to the native method. I think this is likely just a typo.
nodeca/pica,nodeca/pica,nodeca/pica