fix(connectionPlugin): allow first and last to be zero

[leonardodino]

according to the GraphQL Cursor Connections Specification

4.1 Forward pagination arguments

first takes a non‐negative integer.

4.2 Backward pagination arguments

last takes a non‐negative integer.

edit: here's a quick example in the wild

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the patch presented here was done in a quick way to satisfy the spec,
I'm very open to feedback or improvements from the team 😄

[leonardodino]

This seems to not make much sense on it's own, but it's actually really nice for counting edges with totalCount extension in the connection.

right now, as a workaround, I'm using first: 1.

Would be cool to see this merged 🙌

[jasonkuhrt]

Thanks @leonardodino this looks harmless and spec compliant. Let's try it.