[Woodpecker Web] Added index.html that allows log inspection

[mhutchinson]

This is a static HTML version of woodpecker that can be adopted and hosted by log operators. Deploying this to the root of a log, and then opening it in a web browser allows the contents of the log to be easily navigated, entirely in HTML and JavaScript.

As a proof of concept, this PR modifies the sumdb proxy to allow this to be deployed.

[mhutchinson]

This prototype addresses transparency-dev/tessera#89

[patflynn]

as someone who hasn't looked at html or js in a decade this looks like a combination of tidy and a horrific 'leaning-in' to the everything is a div style that I always hated. SInce this is a useful tool, and in the incubator, my thought is that with enough disclaimers its fine to merge this. I'm reasonably confident that it can't do any immediate damage to the log or its users.

I don't really know what we would do to 'graduate' this though. My guess is that it would need a UI dev audit.

[mhutchinson]

@patflynn I agree with your assessment. On the whole, this should be merged, and hopefully inspires a greater rewrite that is verifiable & verified, and has a nicer implementation.

I've added a note that this does not perform verification of the log contents.