:rainbow: Improve look on color screen

[orontee]

Context

It's a shame to stick to a gray scale view on Inkpad color devices.

Analysis

Original weather icons aren't grayscale; See https://openweathermap.org/weather-conditions#How-to-get-icon-URL.
One could replace current icons with the originals and check on color (and also grayscale!) devices the rendering.

See icons/README.md for icons sources, transformation, etc.

[orontee]

Icons proposed by bugs631 on MobileRead forum.

But pbres error with the proposed icons; It works after they're converted to use a color map (conversion done using Gimp) and then icons look wrong on B&W display. One should detect the device capability and convert to level of gray dynamically...

One should also anticipate the impact on dark screen mode and power off logo.

Contribution welcome.

[orontee]

New proposal: https://www.mobileread.com/forums/showpost.php?p=4469541&postcount=14