ScratchCPP Player 0.4.0

Change log:

• Added unsupported blocks warning (#46).
• Added application settings (#21).
• Added theme and accent color options (#19, #20).
• Updated scratchcpp-render to v0.7.1 (https://github.com/scratchcpp/scratchcpp-render/releases/tag/v0.7.1).

Full Changelog: v0.3.0...v0.4.0