Add a more prominent "Donate" button?

I’ve been suggested a few times recently that we make it clearer that one can help Tails by donating money: I’m told that the existing “Contribute” button is not enough, as it makes people think more about technical contribution, hiding the monetary support option.

I see different ways to fix this:

1. Add a “Donate” button to the sidebar, either on all pages, or only on a few selected ones (homepage, download page?).
2. Rephrase the “Contribute” link’s text.
3. Add a “Consider donating or contributing” step to the download page.
4. More?

Note that IMO, this addition is blocked by us adding the Paypal etc. options to our contribute/how/donate page.

Related issues

• Related to #7176 (closed)

Original created by @intrigeri on 7146 (Redmine)