Allows transparent background for JavaFX's WebView. Credit goes to https://gist.github.com/riccardobl/18603f9de508b1ab6c9e
Build the patcher jar-file first using .\gradlew jar, then use the provided run configurations.
JavaFX doesn't support WebViews with transparent backgrounds yet. See JDK-8090547. This workaround enables transparent WebView backgrounds but comes with a big performance penalty since the whole WebView is repainted, rather than just dirty areas.
On 2021-07-03, the CSR JDK-8269848 was opened to officially fix this