Lint tools for WebNN

I've written a couple of local tools to help the authoring/reviewing
process for WebNN <https://github.com/webmachinelearning/webnn> and finally
tossed them in a PR for the other editors to take a look at. They're a mix
of very specific (punctuation and phrases we've decided to avoid, don't
accidentally pull in a new normative reference, etc) and generic (try to
avoid uninitialized variables in algorithms, look for unclosed bikeshed
autolinks, etc), and mostly inspired by fixing spec bugs and adding to our
spec coding conventions.

For now the tools are aimed at authors, not integrated into the automated
publishing process, but that's an obvious future direction.

Jeffrey Yasskin suggested I share this with spec-prod, even at this rough
early stage. I could imagine hooks in the standard spec-prod actions to
invoke per-spec checks that do at least some of this validation.

The PR is here: https://github.com/webmachinelearning/webnn/pull/702