Add page margins option in the webtoon mode

[titan-19]

Describe your suggested feature

I'm simply talking about this option that exists in the suwayomi reader :

Other details

No response

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 latest version.
• I will fill out all of the requested information in this form.

[gotson]

🎉 This issue has been resolved in 1.19.0 (Release Notes)