Now `tox -e docs` will also include the draft changelog for the
next version (locally only).
`CHANGELOG.rst` now only points to the changelog on READTHEDOCS so
sphinx diretives can be used.
Followup to https://github.com/pytest-dev/pytest/pull/6272
Following the lead from tox, use a simple Python script instead of depending
on ``invoke``.
Other changes:
* Some colors using ``colorama``.
* Run ``pre-commit`` before the final commit to ensure everything is neatly
formatted.
* Drop generating local tag: legacy from the time we used ``devpi`` as staging
area, currently we no longer use it, and we should push a
tag from the last HEAD of the PR always to ensure it is correct.