Cuttlebone 0.13.0

Milestone 13: answers after an edit is undone, folding ranges, formatting,
quick fixes, and the exhaustive checks in CI before each release.
Report.

• Fixed: a document edited, closed, and then changed on disk (or
  opened again with other text) had its edits paired with the file's new
  text: a worker crash (checkCrashed) if the file got shorter, and
  possibly wrong answers from the last good check if it kept its length.
  0.10.0 to 0.12.0 have it.
• textDocument/foldingRange: blocks, comment lines and imports,
  from the tokens alone, so also in code that doesn't parse. Kinds and
  rangeLimit as the client says.
• textDocument/formatting: exactly inko fmt's text, from the
  upstream formatter, as one edit; nothing written.
• textDocument/codeAction: quick fixes by diagnostic ID (imports,
  unused imports, variables and results, mut for immutable variables
  and fields), each applied to a copy and checked in full, offered only
  if that leaves no error. For clients with codeActionLiteralSupport.
• Definition at a refused assignment (to an immutable variable or
  field) goes to what the compiler looked up.
• Workspace symbols do less per keystroke.
• Releases wait for the release tier in CI: every test, the latency
  limits as written, and every mutation.
• One patch change (+3 −3, the formatter's Document made public); no
  new extension.

Each archive works with one Inko version, which its name says.
Machine-readable list of the builds, with sizes and SHA-256:
https://github.com/setdef/Cuttlebone/releases/download/v0.13.0/manifest.json
Every release, with its Inko versions and manifest:
https://github.com/setdef/Cuttlebone/releases/latest/download/index.json
(docs/releases.md).