Fix a typo in CHANGELOG.md's release notes for 0.12.

Update changelog for 0.11.3 release and update copyright year.

Update changelog for 0.11.1 release and add a section for Unreleased …

…changes, to prepare for 0.11.2 release.

Upgrade download-artifact action to v4, for compatibility with upload…

…-artifact v4.

Set PyRTL's Python package version from `git tag`.

This avoid keeping the latest version number in two places, `pyproject.toml`
and `git tag`. Simplify instructions in release/README.md.

Rename some GitHub workflow jobs to clarify their purpose.

GitHub actions to automate PyRTL releases to TestPyPI and PyPI.

- Migrade from `setup.{py,cfg}` to `pyproject.toml`
- Add `python-release.yml` workflow
- Prepare a `0.11.0rc1` release.
- Rename `python-package.yml` to `python-test.yml` and upgrade checkout action to `v4`.
- Add release documentation at `release/README.md`
- Use latest python and ubuntu versions for readthedocs.
- Remove the release version number from the sphinx configuration
  (`docs/conf.py`). It doesn't seem to do anything.

Bump patch version: 0.10.1 -> 0.10.2

Bump patch version: 0.10.0 -> 0.10.1

verilog, memory, signed, and other improvements

Bump version: 0.8.5 # VERSION → 0.8.6