v1.0.0-rc6

Use Informal System's fork of Tendermint Core

It seems that the official Tendermint repo has been abandoned and Informal will take over the development with their fork.

@faddat says we should switch to Informal's fork.

Change the required schema for proposal metadata

We're now making title and summary mandatory while other fields optional:

type ProposalMetadata = {
  title: string;
  authors?: string[];
  summary: string;
  details?: string;
  proposal_forum_url?: string;
  vote_option_context?: string;
};

This is because Cosmos SDK v0.47 will introduce mandatory title and summary for all proposals and we want to be consistent with this.