change ChainRegistry types to snake_case to match chain-registry

[pyramation]

Do you think the ChainRegistry class should match the casing of cosmos chain-registry and keep consistent, and use snake_case for fields or should use use camelCase?

The argument for snake_case (which is not the current case we use for ChainRegistry) is for keeping consistent with the JSON objects that are inside of the chain-registry.

Basically we currently have this for ChainRegistry

export declare class ChainRegistry {
    assetLists: AssetList[];
    chains: Chain[];
    ibcData: IBCInfo[];
}

However, the AssetList, Chain, and all else is using snake_case

The issue if we do adopt snake_case is that when we implement classes, it may be weird to have mixed case.

Curious your thoughts here @liujun93