Investigate usage of SVG images instead of PNG

[ann0see]

What is the current behaviour and why should it be changed?

Currently we mainly use png images (even in places where vector based images would be beneficial) . We should discuss if we want to move to SVG instead. This has the advantage of a potentially smaller app, easier size modification. However it's more complex to render them.

Describe possible approaches

Convert new images to SVG. This might introduce a new Qt dependency.

@jamulussoftware/designers I assume you're already working on the new instrument set in SVG format?

Has this feature been discussed and generally agreed?

No. However see: https://github.com/jamulussoftware/jamulus/pull/2508