Dependabot automation needs to include a changelog addition to main

[shaspitz]

Summary

If we want to keep a changelog in main up to date, we'll need the automated dependabot PRs to include the addition of a changelog entry in the unreleased section.

Problem Definition

We need this so humans don't have to manually add entries to a changelog corresponding to automated PRs.

Proposal

Build automation around this idea, see original PR -> #764

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[mpoke]

I don't think we need to add to the changelog the automated dependabot PR. The changelog should contain only bumps of major deps, i.e., SDK, IBC, Comet.