Use QOI format for splash screens

[dc42]

Description

Now that we have facility to write QOI-encoded images to the screen, we should consider encoding the splash screen in QOI format. This could be done as an alternative to the existing format, i.e. if the splash screen data starts with the QOI signature then assume it is in QOI format.

We would need to modify both PanelDueFirmware and the tool that compresses the splash screen. Note, for aesthetic reasons, the splash screen is drawn from bottom to top.