[MINOR] Add a visual indicator of amount of "connectedness" between nodes

[Risto-Stevcev]

Have you checked whether this feature is not already on the project board?
Yes

Is your feature request related to a problem? Please describe.
I want a visual indicator of how many times a node is referenced. For example, if the foo.org roam node references the bar.org node 2 times, and the bar.org node references the baz.org node 5 times, then I want to be able to see a visual indicator that depicts that bar.org->baz.org is more "connected" than than foo.org->bar.org.

Describe the solution you'd like
I was thinking it would be cool if it looked like a neuron, so that the line connecting bar.org->baz.org is thicker than the line connecting foo.org->bar.org, just like a neuron.

Describe alternatives you've considered
I haven't found any.

Additional context
N/A