Problem

There is currently no way to identify assets used for staking on a given chain.

Solutions

1. Asset.features property

Adjacent to a keplr chain config's features: ["stargate", "ibc-transfer", ... ], property, we could add a features property to assets as such:

features: ["stake", "fee", ... ]

2. Chain.staking property

Along the same lines as Chain.fees, we could add Chain.staking as such:

    "staking": {
        "staking_tokens": [
            {
                "denom": "uosmo",
            }
        ]
    },

Notes

The latter may be more conducive for interchain staking, as it wouldn't make much sense to put IBC tokens in the native asset lists.