Document how to publish to Github Pages

[hkBst]

When deploying on Github Pages it is necessary to pass --public-url ${{ github.event.repository.name }} when building with trunk. Might be good to document this. A full example is here: https://github.com/hkBst/tic-tac-toe-seed/blob/main/.github/workflows/deploy.yml

[sak96]

I had some issue with this recently.
passing --public-url /${{ github.event.repository.name }}

adding / before the $ expression helped.
pasting just in case some one faces similar issue.