Python support changes and new endpoints

What's Changed

Adds support for Python 3.10, officially drops support for Python 2.7, 3.4, and 3.5.

Also a bunch of new feature support from underappreciated contributors!

• Update client.py by @kirstaylo in #40
• Implement new routes by @gnuletik in #49
• fix(errors): handle data-explorer responses by @gnuletik in #50
• Add post_action_users to see who liked a post by @inducer in #53
• Update supported Python versions by @bennylope in #54
• Add option to fetch all categories including subcategories by @Sebastian2023 in #59
• Fix getting category details by @Sebastian2023 in #58

New Contributors

• @kirstaylo made their first contribution in #40
• @gnuletik made their first contribution in #49
• @inducer made their first contribution in #53
• @Sebastian2023 made their first contribution in #59

Full Changelog: v1.1.2...v1.2.0