change `ChainRegistry` types to `snake_case` to match chain-registry

Do you think the `ChainRegistry` class should match the casing of [cosmos chain-registry](https://github.com/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`

```js
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