docs: Define the term "open source"

[blacklight447]

trafficstars

Relevant discussion:https://discuss.privacyguides.net/t/what-does-privacy-guides-see-as-opensource/20230

[privacyguides-bot]

This pull request has been mentioned on Privacy Guides. There might be relevant details there:

https://discuss.privacyguides.net/t/what-does-privacy-guides-see-as-opensource/20230/43

[github-actions[bot]]

✅ Your preview is ready!

Name	Link
🔨 Latest commit	93bed9ebe83f17f67cf69b8bb58033ca1f7015d5
😎 Preview	https://2732--glowing-salamander-8d7127.netlify.app/

[blacklight447]

If we move forward with this, we should overlook all pages with opensource requirements and check the currently listed software

[privacyguides-bot]

This pull request has been mentioned on Privacy Guides. There might be relevant details there:

https://discuss.privacyguides.net/t/change-criteria-for-front-ends/20555/2

[jonaharagon]

I'm going to close this because this general page isn't where we should add technical/minor details.

@friadev (re: https://github.com/privacyguides/privacyguides.org/pull/2732#discussion_r1837187399) A better place would be https://github.com/privacyguides/privacyguides.org/pull/2727#discussion_r1726209176 for example.