option to auto clean cached cover

[daminokun]

Describe your suggested feature

Add an option to auto clean old cached cover especially covers not in library. Let us choose the timeframe like weekly, bimonthly, monthly, etc.

Other details

I rarely use neko but the cached had became quite large from neko saving covers while i browse to find new manga to add to library

Acknowledgements

• I have searched the existing issues and this is a new ticket, NOT a duplicate or related to another open issue.
• I have written a short but informative title.
• I have updated the app to the newest version Latest.
• I have checked through the app settings for my feature.
• I will fill out all of the requested information in this form.