Turn README into a contributor + builder landing page

[tmsteph]

The public 3dvr.tech site sends potential contributors directly to this repository, but the README currently opens with “html re-write” and mostly deployment notes. That undersells both the project and the opportunity to contribute.

Goal

Make the README answer, in under 60 seconds:

1. What is 3dvr.tech?
2. Why is it open source?
3. What already exists?
4. How can I run or explore it?
5. What can I contribute today?
6. How do I meet the people building it?

Suggested structure

• 3dvr.tech — Build the future
• Short mission: help people launch real work today while building a practical open-source ecosystem for websites, apps, learning, AI tooling, hardware, and community.
• Links: https://3dvr.tech and https://portal.3dvr.tech
• What exists now: public site, portal, launch/support tools, experiments, customer proof.
• Why open source: user ownership, interoperability, transparency, community contribution.
• Ways to contribute with 3–5 small starter tasks.
• Technical overview: plain HTML/CSS/JS for the main site, paired portal, Vercel deployment topology.
• Keep the existing deployment/billing/testing notes under a developer operations section.

Good first contributions

• Improve contributor onboarding / documentation.
• Pick a small UI/accessibility issue from the open issue list.
• Help clarify the long-term vision without hiding the useful products that exist today.
• Improve tests and cross-device reliability.
• Explore open-source hardware, Debian/Linux, XR, or local-first experiments where they connect to an actual working prototype.

Success condition

A developer arriving from the homepage should immediately understand that this is a living open-source project they can join—not just the source code for a marketing page.