feat: add hacknet network to node.sh join script

[ggutoski]

Use -n hacknet to join the hacknet like this:

KEYRING_PASSWORD=my-secret-password ./scripts/node.sh -n hacknet

Tested on my local machine.

Notes

• For hacknet fetch genesis.json and seeds.txt from this repo instead of s3.
• No support for docker
• No support for validator join