preserve more formatting - EPUB support

currently, we strip out all formatting including line breaks.

is there any way we can preserve certain things to improve the readability?

for example, paragraph breaks, chapter headings, quotes?, italics? (do txt files even have anything?)

each one should be a toggle in the UI. and maybe store the previously used value in the browser

Start by reviewing the UI entry points that control book formatting and the code that currently strips formatting. Check how browser-stored preferences are handled, if at all. Done would require a decided set of formatting options, UI toggles for them, and an agreed behavior for EPUB input, but the issue does not name files or tests.

Written by the indexing model from the issue text.