Add support for polkadot networks

[serejandmyself]

Would be awesome seeing Horcrux make it into the big game (I mean going outside the Cosmos eco).

Right now, it seems, that not all Cosmos founders (latest gitopia - citizen web3 tweets) are aware of the existence of Horcrux. Seems that more touches would make that awareness, and hence - validator security - and hence - user security - at a better level for the whole industry.

[nitronit]

Regarding DOT specific or Substrate SDK. Its lacks remote signer so before that its implemented natively its not really a topic to discuss.

Secondly the code is very much implicitly tailored to CometBFT. To generalise the codebase to a neo-approach suitable other networks (i.e not CometBFT) would be a huge task.

For the time being I think we can close this issue.