README link to Open Austin website is broken

[mrcolbyrussell]

Describe the bug
The link in the README is wrong.

To Reproduce
Steps to reproduce the behavior:

1. Go to https://github.com/open-austin/website-v2-vercel
2. Scroll down to where it says "visit open-austin.org"
3. Click the link

Expected behavior
It goes to open-austin.org

Actual results
It no worke

Additional context
The link goes to https://github.com/open-austin/website-v2-vercel/blob/main/open-austin.org instead. The Markdown needs to be a real URL (like [https://open-austin.org/] where right now it says [open-austin.org] instead) for it to work correctly.