Cuttlebone 0.10.0

Milestone 10: prebuilt binaries.
Report.

• Prebuilt binaries for macOS and Linux, on AMD64 and ARM64 (Linux's
  static, for musl and glibc distributions alike), on each GitHub
  release, built by its own workflow. Each build works with one Inko
  version, which its name says.
• A manifest with each release (manifest.json): per build, the Inko
  version, target, URL, size and SHA-256, so a client can pick the build
  for the user's platform and Inko without scraping
  (docs/releases.md).
• No change to the server's behaviour.

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/v0.10.0/manifest.json
(docs/releases.md).