Add BlRoundedPolygonGeometry

[tinchodias]

Fixes issue #451

TO DO:

• tests needed
• containsPoint: is not precise
• we should cache some calculated values, to avoid repeating the same maths on every new frame
• this is the closed polygon, it's a pity we don't support being an open geometry (a "polyline")
• we may decide to do some refactorings such as merge it with it's superclass

[tinchodias]

An example:

triangleCorners := {
	0 @ 0.
	100 @ 0.
	100 @ 100.
	200 @ 100.
	200 @ 200.
	0 @ 200.
	}.

ref := BlElement new
	position: 50 asPoint;
	geometry: (BlPolygonGeometry vertices: triangleCorners);
	background: Color darkGray;
	yourself.

e := BlElement new
	opacity: 0.75;
	position: 50 asPoint;
	geometry:
		(BlRoundedPolygonGeometry
			vertices: triangleCorners
			radius: 30);
	background: Color red;
	yourself.

e addEventHandlerOn: BlMouseEnterEvent do: [ :evt |
	evt consumed: true.
	evt target background: Color green ].
e addEventHandlerOn: BlMouseLeaveEvent do: [ :evt |
	evt consumed: true.
	evt target background: Color red ].

space := BlSpace new.
space useMorphicHost.
space extent: 300 asPoint.
space root
	addChild: ref;
	addChild: e.
space show.

Screen.Recording.2024-04-08.at.10.02.11.mov