Ytdl-sub

[BACKEND] Set `max_downloads` to `keep_max_files` if present (871)

Implements: https://github.com/jmbannon/ytdl-sub/issues/829

Optimization to not scrape more than what you will keep

[BUGFIX] Properly handle UIDs that have misbehaving chars that get sanitized (870)

Should hopefuly fix both:
- https://github.com/jmbannon/ytdl-sub/issues/843
- https://github.com/jmbannon/ytdl-sub/issues/867

Various sites have unique IDs with characters that get sanitized (i.e. `/`, `:`). `ytdl-sub` was not using sanitized UIDs when looking for files, and would throw an error saying download was missing. This should resolve that issue.

[BUGFIX] Actually fix `subscription_name` with periods in it (861)

Prior PR did not actually work - this actually fixes the bug (https://github.com/jmbannon/ytdl-sub/issues/844) where subscription names would drop periods from them, i.e. Mr. Beast would have the name Beast.

POTENTIAL BREAKING CHANGE
If you have a subscription with a period in its name prior to this fix, this change will make it so your download archive is not found since it uses the subscription name in the download archive file path. To fix, simply change the download archive JSON's name to have the actual subscription name, and not the dropped-period one.

[REFACTOR] Organize variable definitions (860)

[FEATURE] `subscription_map` value (859)

To be used later for advanced presets. For subscriptions in the form of (+ as prefix)


+ Subscription Name:
Music Videos:
- "https://url1.com/..."
Concerts:
- "https://url2.com/..."


Stores all the contents under the subscription name into the override variable
``subscription_map`` as a Map value. The above example is stored as:


{
"Music Videos": [
"https://url1.com/..."
],
"Concerts: [
"https://url2.com/..."
]
}


Advanced scripting is needed to dissect this Map variable into a usable preset

[BUGFIX] Fix periods not working in subscription names (857)

Fixes the bug (844) where subscription names would drop periods from them, i.e. Mr. Beast would have the name Beast.

POTENTIAL BREAKING CHANGE
If you have a subscription with a period in its name prior to this fix, this change will make it so your download archive is not found since it uses the subscription name in the download archive file path. To fix, simply change the download archive JSON's name to have the actual subscription name, and not the dropped-period one.