some .epub files miss encoding tag (and change encoding option is not available)

[Alexqwesa]

In some epub files the line <?xml version='1.0' encoding='utf-8'?> in html files is missing.

So, files like https://github.com/Alexqwesa/files_for_bug_reports/blob/main/epub-wrong-encoding.epub are shown incorrectly

Possible solution:

1. change default encoding to UTF8
2. allow change encoding for epub files
3. some other options?

To fix problem: sometime you only need tag <?xml version='1.0' encoding='utf-8'?>, but sometimes <meta charset="UTF-8"> is also required...

kchmviewer version 8.0 built at Mar 20 2023 12:00:00 - openSUSE 15.5

[Alexqwesa]

the content of provided file look like this:

Next 2 lines just contain apostrofes: ’’’’’’’’’’’’’’’’’’’’’’’’’’’’’ '''''''''''''''''''''''''''''

[brjsp]

This is possibly a regression due to Webengine — i haven't ever noticed this problem with the QtWebkit Windows build.