Support for line level labels

[pascalberger]

Labels can currently be created for a range or location consisting of line and column. It would be useful to have the possibility to create a label for a whole line. Currently this is possible by either set column to 1 or appropriate length or span if this information is available.

API could look like this:

report.AddDiagnostic(
	new Diagnostic("Fix formatting")
        .WithLabel(new Label("Example/Files/Program.cs", new Location(42), "Code should not contain trailing whitespace")
            .WithColor(Color.Yellow)));

Labels affecting a whole line can either by drawn across the whole line:

Or by marking the linke to the side: