relayer config: add support for fuji

[teterabOb]

Context and scope

We are currently at the Avalanche Summit Hackathon. To implement our L1, we are using Ava Cloud. Although interoperability is configured, Ava Cloud does not reflect the setup as complete.

I deployed a contract to send messages from our L1 using Teleporter, but the messages are not being delivered successfully. I believe the issue lies in the relayer not being properly initialized.

One potential solution is to configure a relayer using the avalanche-cli, but this tool only supports local networks.

Requirement

Add support for the fuji testnet in the relayer configuration options.