Add config to disable link underline

[ben-gooding-sky]

Happy for feedback on the implementation

linkColor is duplicated, but should be backwards compatible

Examples

[jeziellago]

Could you take the advantage of having the new LinkStyle and use the color from there, using the linkColor as fallback, to avoid inconsistence and keeping backward compatibility?
Something like:

val currentLinkColor = if (linkStyle.color != Color.Unspecified) {
    linkStyle.color
} else {
    linkColor
}

[jeziellago]

Could you also add examples for links with/without underline in the project sample?