Display relationship cardinality

[louisremi]

I love this plugin! It's a great addition to Strapi to help onboard new developers.

It would be super useful to have "1" or "n" displayed next to the origin or end of the curve that materializes the relationship, to know exactly what kind of relationship we're dealing with.

[BasVerdoorn]

Very cool plugin. The only thing I still miss is being able to see the type of relationship. An idea could be to give each type of relationship a different color or symbol.

@romanmandryk