Technical - Create and use an extension for disabled/enabled coloration

[paulinea]

This is not the purpose of this MR but there is now a lot of copy(alpha = ContentAlpha.disabled) in the code. I don't know if this a good idea but we could add the following extensions:

val Color.disabled: Color
    @Composable
    get() = copy(alpha = ContentAlpha.disabled)

@Composable
fun Color.enabled(enabled: Boolean) = if (enabled) this else disabled

tint = OdsTheme.colors.onSurface.enabled(enabled = enabled)

Originally posted by @florentmaitre in #300 (comment)