Migrate to using pixi for CI and development

See merge request !23

fix(ruff): set to line length back to 88 as used originally

See merge request !22

That's the default for ruff but it makes it clearer that this
is what we want.

Adds support for pixi development installation

See merge request !21

Use ruff to replace black, isort, pyupgrade, docformatter and flake8 qa rules

See merge request !20

Use hatch and versioningit for modern project management

See merge request !19