Service specific downloader arguments

[DebugPanda]

Hello dev,

Hope you're doing fine and good.
I'd like to request a new feature called "Service custom arguments" which is like similar to dl options predefined in unshackle.yaml

The only change is, instead of triggering the custom options that we set for dl in a general way, we need to implement it for specific services too. For example, some services limit their connection, so n_m3u8dl_re thread counts and dl's workers might not work.

Like this.
Service_custom_arguments:
Example_service:
n_m3u8dl_re:
thread_count: 8
add_proxy: True

[Sp5rky]

Should be easy enough to implement, will look at this.

[DebugPanda]

Should be easy enough to implement, will look at this.

Thank you dev.

[Sp5rky]

Keeping it open till I've pushed the fixes, (so I know what I have left to do :))

[DebugPanda]

Oh, ok. As you wish.