Allow users to support you with Bitcoin Cash

Hello DarkReader peoples,

Recently another dev, @EchterAgo introduced me to DarkReader. I have been using it every day since then and it's such a huge improvement for someone like me that gets headaches from bright lights. I want to support your development so I made an account on OpenCollective. However they are limited to credit cards, paypal and bank transfers which do not work for me. Could I beg you to add a Bitcoin Cash donation method so that I can support you?

The easiest way is just to put a single receiving address / QR code (edit - you can get that with [Electron Cash](https://electroncash.org/)). If you want to do some kind of integration, there are a number of options (https://business.bitcoincash.com/merchant-solutions).

In any case, thank you for DarkReader. It is a serious quality of life improvement for people like me.

No files or tests are named. Inspect the Dark Reader website's existing donation or support content and the OpenCollective payment methods first, then determine where a Bitcoin Cash address or QR code would belong. Done means the new donation method is presented clearly and its links or payment details work.

Written by the indexing model from the issue text.