Allow ChainId as string

[toschdev]

Proposal: ChainId should accept a string

Current behavior: ChainId allows only base-10 numbers

Desired behavior: ChainId accepts a string

Use case: The current standard used by all known CosmosSDK blockchains are string as ChainId. E.g. cosmoshub-3

Even though the standard for Ethereum blockchains is using a numeric ChainId, in the Cosmos Ecosystem strings are mostly used and expected to be used in the future. Supporting string ChainId's would make the integration seamless for many projects.

Requests may be closed if we're not actively planning to work on them.