WebKitGTK 2.53.4 released!

This is a development release leading toward 2.54 series.

Implemented batched painting in skia compositor, which improves performance when there are many layers that can be painted in the same operation.
Avoid unnecessary clips when possible in skia compositor.
Fix synchronization issues between main, scrolling and compositing threads causing glitches while scrolling in some cases.
Limit the damage region of the scrollbar to the region actually painted.
Add support for image/webp to canvas.toDataURL().
Expose search inputs as WEBKIT_INPUT_PURPOSE_SEARCH.
Add User-Agent quirk for HBO Max.
Fix several crashes and rendering issues.

Thanks to all the contributors who made possible this release.