Better captchas

[ara4n]

@webmind kindly recommended a bunch of non-Google captchas to avoid the Goog dependency (and possibly improve a11y):

QuestyCaptcha, mediawiki plugin we use for wikis. It depends a lot on
what kind of questions you ask. Questions which are simple but do
require some knowledge about the project seem to work best.
https://www.mediawiki.org/wiki/Extension:QuestyCaptcha

We use an ASCII art based one on a drupal-based platform. We deployed it from the start and never had any spammers.
https://www.drupal.org/project/captcha_pack

I haven't tested this one, but someone mentioned it to be when
discussing accessible captchas, this one supports audio:
https://packagist.org/packages/dapphp/securimage

[ara4n]

#3606 is now the main bug for this