[Feature request] feature to download all of playlist

[pipepipeaccount]

Checklist (Your issue will be automatically closed if you delete this part)

• I make sure that there are no existing issues - open or closed - which I could contribute my information to.
• I believe this feature request will benefit more than 10% of users, not just myself.

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** Description
A feature to download all of playlist videos at once rather than video by video, would be quite helpful and time saving, when traveling where there is no WiFi. Many thanks!

[InfinityLoop1308]

Will be added in 4.4.0.
Preview version can be get here.