Deckle v0.3.1

See CHANGELOG.md for what changed and README.md for install notes.
Updating from 0.2.x? Install this version once by hand; later versions update from inside Deckle (Settings → About). Windows: if you used the .msi, uninstall it first.
macOS: signed with a Developer ID and notarized by Apple.
Windows: code-signed by Casa Vargas LLC (Azure Artifact Signing).
Requires Kindle Previewer 4 (free, from Amazon).