[ascon/doc] add specification in markdown

[m-temp]

This adds the https://docs.google.com/document/d/1hTnnhm5SoVCBYWObaTSfTLuKE07erR1ZapirLuR6YGU/edit as markdown.
See #22178

[nasahlpa]

Text looks fine for me. However, I think the formatting of the markdown file needs to be improved, there are a lot of double line breaks and unintended text blocks.

[andreaskurth]

Thanks for this conversion to Markdown, @m-temp. This is an approved RFC, so LGTM. Only one thing should be changed, please: Most SVGs are currently much larger (width and height) than their content; could you please crop the 'page size' to the content?

[m-temp]

Thx @andreaskurth for the review!

Thanks for this conversion to Markdown, @m-temp. This is an approved RFC, so LGTM. Only one thing should be changed, please: Most SVGs are currently much larger (width and height) than their content; could you please crop the 'page size' to the content?

Ups. looks like the svg export of google-docs/draws adds some space here.
I'll change that!

[m-temp]

I changed ASCON => Ascon. And did an auto-generated update on the register.md to match the latest improvements.