use URL references to protocol from README

[zancas]

No description provided.

[daira]

If you look at the rendered version of README.rst which is https://github.com/zcash/zips/blob/publish/rendered/index.html , it does point to those URLs, but in a way that automatically uses the correct URL for light and dark modes. This PR will break that, admittedly only because the regexes at

zips/render.sh

Lines 80 to 81 in 6b9931b

	's|<a href="[^":]*">Protocol Specification</a>|<span class="lightmode"><a href="https://zips.z.cash/protocol/protocol.pdf">Protocol Specification</a></span>|g;
	s|\s*<a href="[^":]*">(dark mode version)</a>|<span class="darkmode" style="display: none;"><a href="https://zips.z.cash/protocol/protocol-dark.pdf">Protocol Specification</a></span>|g;

are a little fragile. The regexes could be fixed.

The local copy of README.rst is supposed to point to the local rendering of protocol.pdf and protocol-dark.pdf, which it does. The GitHub README.rst rendering is supposed to point to the GitHub page for the rendering. Currently, when you're looking at the main branch it points to
https://github.com/zcash/zips/blob/main/rendered/protocol/protocol.pdf which is wrong (it's a 404). It should be https://github.com/zcash/zips/blob/publish/rendered/protocol/protocol.pdf . This regressed when the renderings were moved to the publish branch.

This PR would fix that but at the expense of the local file no longer pointing to the local rendering, which I don't like. OTOH, many of the other links are broken in the local rendering. So that can probably be fixed separately. When I get around to it, I'll fix the regexes mentioned above and then merge. In the meantime, NACK because of the regression in automatic light/dark mode selection.

[daira]

Moving to draft until I have time to fix the regexes in render.sh.