📈 chore(demo-site): add analytics and privacy policy

[welpo]

I'm making two important updates to the tabi demo site with the aim to improve the project while maintaining transparency and respecting user privacy.

Adding GoatCounter Analytics

To better understand how users interact with the demo site, I'm implementing GoatCounter, an open-source and privacy-friendly analytics tool. The data collected will be non-identifiable and solely aimed at providing insights for improving user experience.

• Self-Hosted GoatCounter analytics.
• Public Dashboard: I'm introducing a public dashboard, accessible here, to share the same insights with the community. In other words: all data collected is 100% public.

New Privacy Policy

I'm also introducing a new Privacy Policy, explaining how the data is collected (for analytics and comments).

The privacy policy has been designed to be comprehensive and transparent. You can read it here.

Benefits

• Improved understanding of user needs and behaviour. It could help in detecting missing translations that would benefit a large group of potential users; decide whether a mobile or desktop focus should take precedence; and provide data-based answers to "should we support this old browser?" or "is it a good idea to use this new feature for browsers?".
• Greater project transparency.
• Clear guidelines on data collection and usage.

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I'm committed to transparency.

I'm also open to changing my mind about the analytics—I did a lot of thinking before opting in favour.

I'm 100% against tracking, but I think analytics, through GoatCounter, with no data shared with any third parties and no identifiable information stored, are both ethical and potentially benefitial to the tabi project.

I value community input and would love to hear any thoughts, concerns, or suggestions you may have regarding this update. Feel free to comment on this PR or reach out directly.