[webkit-qt] QtWebKit 5.212.0 Alpha 4

[Konstantin Tokarev]

New release is now available! Source tarballs and binaries are available at https://github.com/qtwebkit/qtwebkit/releases/tag/qtwebkit-5.212.0-alpha4

### New APIs

* `QWebSetting::ErrorPageEnabled` - `true` by default, allows to disable built-in error pages if they are not desirable

### Improvements

* [CSS Compositing](https://www.w3.org/TR/compositing-1) is now supported
* Push is enabled by default for HTTP/2 requests
* QtWebKit does not require Python 2 anymore for building and can use Python 3 instead
* QtWebKit won't be eager to pick bitmap fonts as a suitable choice for standard font families
* More appropriiate hinting option for web fonts is used

### Bug fixes

* Fix memory leak in [CustomEvent](https://developer.mozilla.org/en-US/docs/Web/API/CustomEvent/CustomEvent)
* SVG fragment identifier is not respected if it is a part of an HTTP URL  (#818)
* Context menu actions for images in Resources tab of inspector use blob: instead of original URL (#899)
* Always enable JavaScript for QWebInspector (#566)
* Inspector UI: Only selected item is painted in Styles combobox (#262)
* Inspector should inspect itself in DEVELOPER_MODE only (#444)
* fast/gradients/css3-color-stop-invalid.html - box is green instead of white (#230)
* Work around [QTBUG-77308](https://bugreports.qt.io/browse/QTBUG-77308) when using Qt < 5.14
* Fix compilation errors with ICU 65.1 and Qt 5.14
* Fix compilation when QPdf is disabled in Qt
* Fix compilation with MinGW for x86_64 target

### Third-party software updates

Windows binaries are shipped with `ICU 65.1`, `libxml2 2.9.10`, `libxslt 1.1.34`, and `libjpeg-turbo 2.0.3`.

## Sponsors

This release is sponsored by:
* dizmo AG
* Florian Apolloner
* Movable Ink and Michael Nutt
* ScrapingHub

-- 
Regards,
Konstantin