Bump python support from 3.7–3.9 to 3.8–3.10

[bdewilde]

Description

• add support for PY3.10, drop support for PY3.7
• make PY3.8 the standard version used in workflows, packaging, etc.

Motivation and Context

Python 3.10 was released earlier this year, and since spacy (not to mention numpy, etc.) supports PY3.10, textacy should too. On the other end, we're dropping PY3.7 support to align with numpy's supported versions convention and to take advantage of improvements made to typing in PY3.8.

How Has This Been Tested?

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation, and I have updated it accordingly.