Added few more participants

[vimode]

Thanks for contributing to the Hacktoberfest Swag List 😃 🎉! Before submitting your pull request, please check off as many of the items below as you can:

1. I have read the Contributing.md file and formatted this PR correctly
2. I'm not adding a company from the blocklist
3. I make sure to fix things promptly if an error or suggestion comes up

Thanks and Happy Hacktoberfest! 🎉
Tagging @crweiner to take a look. 👀

---

This PR adds Hugging Face, Prefix.dev, HaystackAI and Sia Foundation to the list.

It also fixes the heading hierarchy for QuestDB.

[netlify]

✅ Deploy Preview for hacktoberfest-swag-list ready!

Name	Link
🔨 Latest commit	e68dfb7
🔍 Latest deploy log	https://app.netlify.com/sites/hacktoberfest-swag-list/deploys/6528bade2625cb0009060f48
😎 Deploy Preview	https://deploy-preview-824--hacktoberfest-swag-list.netlify.app/list
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify site configuration.

[ghost]

👇 Click on the image for a new way to code review

Legend

[codeclimate]

Code Climate has analyzed commit e68dfb7 and detected 0 issues on this pull request.

View more on Code Climate.

[crweiner]

@vimode, I would have been lost without you this year. Thank you so, so, so much for all of your time curating companies to add to the list, opening new Issues, submitting incredibly helpful PRs like this, and reviewing other people's PRs. You have been an incredible help and I deeply appreciate it. ❤️

Thank you for making this a great Hacktoberfest!

[vimode]

You're welcome!

Happy Hacktoberfest! 😄