v3.1.0

Added

• Block tunes support: the official textVariant tune
  (@editorjs/text-variant-tune) wraps block HTML in the editor's own
  cdx-text-variant--<citation|call-out|details> markup, and the official
  footnotes tune (@editorjs/footnotes-tune) appends the footnote texts as
  a cdx-footnotes list. Applied generically to any block type.
• delimiter.tag config: "hr" renders a semantic <hr /> instead of the
  historical default <br />.
• GitHub Actions CI (typecheck, tests, build on every push/PR).
• engines: { node: ">=18" } and a ./package.json exports entry.

Fixed

• Images without a caption now render alt="" and omit the <figcaption>
  instead of emitting literal undefined (only affected previously-broken
  output).
• Header levels are clamped to h1–h6; a malformed level can no longer
  inject markup into the tag name.