* Add WebP support

* Remove the changes to the tooltip

refs: https://github.com/tootsuite/mastodon/pull/9879#pullrequestreview-199312528

To improve the way super tall or super ride images are treated, the
numbers remain the same, 1280x1280 and 400x400, but if an image
is less in one dimension than the other, the other can become larger

Thanks to @WAHa_06x36@mastodon.social for the tip

Fix #7748

Fix #7487

Fix #7383

- Use URL.createObjectURL (replace from FileReader)
- Use HTMLCanvasElement.prototype.toBlob
  (replace from HTMLCanvasElement.prototype.toDataURL)
- Use Promise (replace callback interface)