Ability to set saved picutres folder as a subdirectory of user-set external storage folder.

[KraXen72]

Describe your suggested feature

spun off of https://github.com/tachiyomiorg/tachiyomi/issues/9951 Please add a toggle in the setting that makes it so that pages from manga saved with the "Save Image" function will end up in a Pictures subfolder of the user-set external storage.

Other details

low priority

Acknowledgements

• [X] I have searched the existing issues and this is a new ticket, NOT a duplicate or related to another open or closed issue.
• [X] I have written a short but informative title.
• [X] If this is an issue with an extension, I should be opening an issue in the extensions repository.
• [X] I have updated the app to version 0.15.0.
• [X] I will fill out all of the requested information in this form.