v1.1.0

A parse rule that declines no longer blocks the ones behind it. Rules are
tried in priority order and the first match wins — but a rule whose getAttrs
returned false ended the search rather than passing the element on. One broad
rule could therefore shadow every narrow one behind it: textStyle claims
span, declines a span with no inline style, and span[data-comment],
span[data-field], span[data-hashtag] and span[data-math] never got a turn.
The symptom was a comment mark that vanished on the way in whenever textStyle
happened to be in the same schema. Declining is now "not a match", and the walk
continues.

Extension stylesheets no longer decide a document's vertical rhythm.
embedCSS, mathCSS, youtubeCSS and pageBreakCSS each set a fixed
margin: 1em 0 on their node. Adjacent margins collapse to the larger of the
two, so one node with an opinion pulled every gap around it out of line with
whatever the host had set. They now read var(--matra-block-gap, 1em) — the
default is unchanged for anyone who sets nothing, and a host that sets
--matra-block-gap on its editor brings every extension into step. Page breaks
read --matra-page-break-gap, which defaults to 1.5em as before.

Twitch players and clips can be embedded. player.twitch.tv and
clips.twitch.tv join the default allow-list. twitch.tv itself does not, for
the same reason the rest of Google is not on it.