Change Link extraThickness

[thiago4455]

Currently the extraThickness passed to ed::Link::Draw is hardcoded. It would be nice to have a setting so that can change. I feel like that 4.5f can bee too much.

imgui-node-editor/imgui_node_editor.cpp

Lines 888 to 895 in e78e447

	else if (flags & Selected)
	{
	const auto borderColor = Editor->GetColor(StyleColor_SelLinkBorder);
	drawList->ChannelsSetCurrent(c_LinkChannel_Selection);
	Draw(drawList, borderColor, 4.5f);
	}