v0.6.3

Added

• Added optional hidden property/attribute which prevents a file from being
  displayed in the tab bar.

• Added support for JSON files with syntax highlighting.

• Added extends property to JSON config file, an optional URL of another JSON
  config file to extend from. Useful for setting side-wide defaults.

Fixed

• Fixed bug where editor did not immediately switch to newly created files.

• Fixed bug where label was ignored in tab bar.