add support windows-1251 encoding

[нездалисько]

feed-extractor does not understand windows-1251, which is still required for some sites.

[Dong Nguyen]

@uandreew could you share a few feeds with that character encoding?

[нездалисько]

@uandreew could you share a few feeds with that character encoding?

It will be hard to find a few, but I know one with this encoding. https://pravda.com.ua/rss using cp1251 encoding

[Dong Nguyen]

thanks, it will help to debug the issue.

[Alexander]

Yet another example with the koi8-r encoding: https://www.opennet.ru/opennews/opennews_sec.rss