Updated settings icon, rounded the circular play/pause icons, and addition of a new high contrast theme. Would be good to get feedback on the high contrast theme at this stage, as my intention is to use it as the basis for other 2-colour themes.

One issue I'm aware of is the charge indicator when recoloured to black is not very legible on the black battery icon. I am planning on adding an additonal outline image that can be recoloured to the background colour to make it stand out more. Happy to fix that in a later PR or I can add it now but it will take a bit of work.

Reviewed-on: https://codeberg.org/cool-tech-zone/tangara-fw/pulls/100
Co-authored-by: ailurux <ailuruxx@gmail.com>
Co-committed-by: ailurux <ailuruxx@gmail.com>