Allow KRunner plugins to render QML

Hi, KRunner is one of my favorite plasma tool so far, it takes a really important place in my workflow and so far it has been a pleasure to use.

Recently I found a macOS “alternative”, or at least similar software, called Raycast, that has one key element that I find missing in KRunner, plugins can render their own UIs, here using J/TSX. While the current implementation is pretty powerful, I think having the ability to render our own QML forms and display them into KRunner would be a great addition and make it more aesthetically pleasing that a simple list.

Cheers, Luna