Include 'deletable' property with EdgeProps and NodeProps

[TimmyTango]

Please describe the feature that you want to propose

The deletable property exists on Nodes and Edges, but isn't exposed to NodeProps and EdgeProps. This means you can't use the deletable property for conditional rendering for Node and Edge types.

In my specific case, I want to hide the delete icon I normally show on Edges in my EdgeType if deletable is false. I tried to access deletable anyway, hoping it was just at the type level, but it's always undefined.

As a workaround, I'm adding my own deletable property in my Edge's data property.

[peterkogo]

Thanks for bringing this up! That actually is a viable use case. I will open a PR for this.