Add minimal CI validating that this repo stays Python 3.8 compatible

[joanise]

Since we decided to stay compatible with Python 3.8, let's have CI minimally validate it remains true.

While doing this:

• noticed that ctc-segmenter did not support -h, so added it;
• noticed that this submodule does not use pydantic, and therefore the mypy pydantic plugin failed to even load;
• bumped our actions to the latest since we're now getting warnings about Node 16 being end-of-life.

In everyvoice, we use conda to install Python, but this module does not need conda, and it takes longer to setup with it, so here I'm just using the regular action/setup-python.

[github-actions]

CLI load time: 0:00.27
Pull Request HEAD: 33c0b0ea7b4e27d5e63fb1319205adb7d829f261
Imports that take more than 0.1 s:
import time: self [us] | cumulative | imported package
import time:      1047 |     111437 |         typer.rich_utils
import time:      1927 |     114346 |       typer.core
import time:      1460 |     139839 |     typer.main
import time:       406 |     174811 |   typer
import time:       490 |     182362 | aligner.cli

[roedoejet]

Awesome, thanks @joanise !