[Docs] Create a prominent section on leo devnode

[vicsn]

📚 Documentation

Here: https://docs.leo-lang.org/guides/test

Should also note that deployments without certificate don't check for the circuit deployment limit, so leo synthesize should be ran separately in the testing workflow.

CC @alexanderkim11

[mohammadfawaz]

I transfered this issue from leo to leo-docs-source so that @AleoAlexander can keep track of it better.