`changelog.rst` is difficult to find

Can you please link to https://github.com/dbcli/pgcli/blob/main/changelog.rst (or perhaps a tagged latest-release version) from pypi (by adding a setting to `pyproject.toml`) and https://www.pgcli.com/docs so that we can see what goodies we're getting this time.

Start with pyproject.toml and the documentation at https://www.pgcli.com/docs. Check how the PyPI project links and docs navigation are configured, then add discoverable links to changelog.rst or the latest release changelog in both places and verify that they resolve correctly.

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