add bridge information to parent field

[ligi]

currently the parent field looks like tis:

{
...
"parent": {
 "type" : "L2",
 "parent": "eip155-1"
}
}

I suggest we add a "bridge" field. Just wondering if we need more than just an URL.

[ligi]

@khai911013 ?

[ligi]

I think we make it future proof by making it an array of objects like this:

{
...
"bridges": [ {"URL":"https://bridge.arbitrum.io"} ]
}