2024-07-23: v2.2.0

• Added a spec attribute version check (checks that version
  attributes are less than or equal to the file's spec attribute)
• Added a TR-106 naming rule check, including rules for vendor extensions
• Added a check for CWMP models that define commands or events
• Added a table / num-entries parameter version check (they should always
  have the same version) plus warn if non-tables have num-entries
  parameters
• Added checks for Alias parameters that aren't in tables or aren't
  unique keys
• Added checks for list-valued defaults (they must be in square
  brackets, and scalar defaults must not be in square brackets)
• Added an "object default" validity check
• Added a check for signed types that could be unsigned
• Added difflint checks for illegally-removed model or profile items
• Supported DT (Device Type) instances
• Improved the diff transform's handling of deleted attributes and
  elements
• Allowed component references to inherit their version attributes,
  which means that the version can usually be omitted
• Added some more output formats, e.g. a difftext format that outputs
  an easily-searchable list of differences, and a path format that
  outputs the path names for all objects, parameters etc.
• Added auto-generated HTML text for writeOnceReadOnly and
  activeNotify="canDeny" parameters
• Fixed a command and event argument ordering bug that caused confusing
  placement of top-level argument parameters in HTML
• Fixed {{datatype}} expansion problem that could include information
  about the parent object rather than about the data type
• Fixed bug in the XML output format, which could wrongly omit version
  attributes from generated XML
• Added logic to the XML output format to use the latest encountered
  DM Schema version in generated XML files
• Fixed HTML formatting problems affecting patterns and defaults
  containing special characters
• Fixed dark-mode hover-link and background colors
• Avoided some tool crashes, e.g., when an object has been defined before
  its parent
• Fixed the handling of the non-standard "absolute" path scope (it was
  being ignored)
• Improved MediaWiki markup compatibility (MediaWiki markup will continue
  to supported, but markdown is preferred)
• Documented the decimal data type (it was already supported, but the
  documentation said "TBD")
• Exit code is now the number of reported errors (useful in scripts)
• Various internal improvements that are only visible to plugin authors
  (the plugin interface has not yet been officially documented)
• Improved the documentation on running pandoc to convert markdown to
  HTML
• Fixed the file name in XML Schema validation error messages