Support more font weights

[Windisch94]

As for the documentation of the flutter font weight it would be helpful if we can create a mapping between more fonts as Bold and Medium (as for now)

The flutter font specifies the following: (all except thin exist in figma also)
/// * [w100]: Thin, the thinnest font weight. (dont exist in figma)
/// * [w200]: Extra light.
/// * [w300]: Light.
/// * [w400]: Normal. The constant [FontWeight.normal] is an alias for this value.
/// * [w500]: Medium.
/// * [w600]: Semi-bold.
/// * [w700]: Bold. The constant [FontWeight.bold] is an alias for this value.
/// * [w800]: Extra-bold.
/// * [w900]: Black, the thickest font weight.

maybe the figdart plugin can handle these weights also - thanks!