Separate Extension icons for dark/light mode

[daimor]

Is your feature request related to a problem? Please describe.
Yeah, some of the icons, may look good on a light theme, but a dark theme may require some changes in colors.

Describe the solution you'd like
add an ability to define different icons in metadata.json

{
  "icon": "compny-logo.svg"
}

Additionally support for something like this, but keep previous supported

{
  "icon": {
    "dark": "compny-logo-dark.svg",
    "light": "compny-logo-light.svg"
  }
}

I did not get when used labels from Dockerfile, and not sure if it would even need there
com.docker.desktop.extension.icon=
com.docker.desktop.extension.icon.light=
com.docker.desktop.extension.icon.dark=