Add Linea testnet and mainnet to Dashboard’s known networks

[OnlyOneJMJQ]

We should support our ConsenSys fam in Linea by adding their network to our list of known networks in Dashboard. Both a nice touch and adds clarity for Linea devs.

While we're in there, perhaps it's worth setting a standard way to represent test and dev networks (see screenshot). Something like a badge below a consistent network icon? Happy to separate this part of the issue if there's much discussion, since the Linea networks can be added without this consideration.