preference system for QImageIOPlugin

I created a QImageIOPlugin for SVGs that uses Resvg instead of QSvg but unfortunately it cannot be installed side by side with the qsvg plugin because there appears to be no system through which to express that the resvg plugin should be preferred over the qsvg plugin.

From the docs:
"If several plugins support the same capability, Qt will select one arbitrarily."

Possible trivial solutions:

• sort the plugins by name, pick first match
• add a key to the json blob that expresses explicit preference over qt plugins (that leaves competing third party plugins out in the rain though)
• add a score key to the json blob, pick the highest scored plugin (that may just result in third party plugins picking an insanely high score to outscore each other )

https://invent.kde.org/sitter/qresvgimageiohandler