* docs(logs): Mimick argparse option default format
I find it more readable to use punctuation to separate technical information, such as
required vs optional or default values, from narrative description. Follow argparse's
lead, and put such information in parens following the narrative description.
* docs(usage): Consistent structure, clarifications
* docs(config): Clarify persist_logs behavior/opts
Clarify the `persist_logs:` options per [Discord discussion](https://discord.com/channels/994270357957648404/1409161361853780060/1409602529460879431).
Adds a new mechanism to limit subscriptions' number of videos to an explicit number (only supported date ranges prior to this).
Example usage:
```
output_options:
keep_max_files: 10
```
will only keep 10 videos at max.
In addition:
- `keep_max_files` is bundled into the `Only Recent` preset and can be used via setting the `only_recent_max_files` override variable (see examples or README for usage).
- Changed the `date_range` variable name to `only_recent_date_range` for more clarity. Usage of `date_range` will continue to work.
