Missing schema documentation for 'color' and 'iconUrl'

[XDelta]

These 2 props were added in this commit and not yet documented
neos-modding-group/neos-mod-manifest@73fd82a

[ljoonal]

• iconUrl should be a documented to be a publicly accessible URL that resolves to an image file (preferably in a common format like JPG/PNG, and its suitable for use as an icon, aka small filesize instead of an absurdly large image).
• color Should be documented to be the hex color without a leading # character

Both of these should not be marked as mandatory, and their usecase of customizing how the mods information might be displayed should be noted.

[Psychpsyo]

Documenting these now.