New feature "SDoc fragments from files" and improvements in the infrastructure

What's Changed

• tasks: tests-unit: allow running in focused mode by @stanislaw in #628
• Code climate: remove unused code "ng_sections" by @stanislaw in #631
• new feature FRAGMENT_FROM_FILE by @BenGardiner in #629
• requirement: use multiline value for None values in meta fields by @BenGardiner in #633
• tasks: reduce repetition of "one_line_command" by @stanislaw in #635
• tasks: fix broken mypy task by @stanislaw in #636
• Poetry: upgrade and update requirements.txt by @stanislaw in #637
• link_health: check dead links in strict.sdoc by @stanislaw in #638
• tasks: replace Poetry with plain setup.py by @stanislaw in #640
• tasks: simplify setting up dependencies by @stanislaw in #642
• Bump version to 0.0.22a1 by @stanislaw in #643
• setup.py: include requirements.txt to the egg by @stanislaw in #644
• tasks: "release" task by @stanislaw in #645
• tasks: make the venv types explicit by @stanislaw in #646
• CI: daily integration test by @stanislaw in #647
• docs: document the new development workflow without Poetry by @stanislaw in #648
• docs: update Docker instructions by @stanislaw in #649

Full Changelog: 0.0.21...0.0.23

What's Changed

• setup.py: fix copying of the HTML files by @stanislaw in #655

Full Changelog: 0.0.21...0.0.23

What's Changed

• setup.py: fix copying of the HTML files by @stanislaw in #655

Full Changelog: 0.0.22...0.0.23