Markup: PDF generation

[gesa]

Tried to keep the css together but it doesn't feel super logically grouped so I wound up rearranging everything. Sorry future git-blamer. Units of measurements are all over the place, here's what defines them:

• mm for page-related units
• pt for text-related units
• em for horizontal units
• ex for vertical units

Highly specific rules come from a loyalty to the Ecma specification template first, previous years' standards second.

There should be no changes that impact screen rendering. Any changes to the primary stylesheet come from inline styles that existed in both ECMA-262 and ECMA-402.

The cover SVGs aren't really used by ecmarkup directly, but are rather to be viewed as source files for the two specifications.

[gesa]

See https://github.com/gesa/ecmarkup/commit/c6b6b9cf6d70c9a2cd9c11941b8236bf1b7b7bbf#comments for the most important detail of this PR.

[michaelficarra]

@gesa Have you tested both with and without --multipage?

[gesa]

@michaelficarra I have, I’ve generated web versions of ecma402, ecma262 (multipage), and temporal.

[gesa]

@syg , @michaelficarra : following up to get this merged when y’all have a chance