Sunstone v0.25.1

Added

• Fonts are configurable in config.json, separately for the interface, the
  Concept text and code: a family, a default size, and optionally font files
  placed next to the config. Zoom scales the configured sizes. See
  docs/interface/fonts.md.
• Sunstone Web reads the same config.json format, colours included, from the
  file SUNSTONE_CONFIG points at. The settings are already in the first
  rendered page, and changes show on the next page load.
• Every item in the editor, Explorer and table context menus has an icon, and
  the table menu's delete items are styled as destructive, like Delete in the
  Explorer.

Fixed

• The Frontmatter Region shows for index.md and log.md again.
• Selecting text inside a table cell keeps the selection, and Find highlights
  its matches inside table cells.
• Sunstone Web keeps the open Concept open when the repository behind it
  changes (a git swap), instead of jumping back to the start page.