Additional improvements to the generated dictionary files

[vaitkus]

There are three minor issues that should be addressed in the generated dictionary files.

Explicit dictionary licensing

Dictionary files should contain explicit licensing declaration. In other IUCr dictionaries this is done by:

1. Adding an SPDX comment on the second line, after the CIF 2.0 magic number comment, e.g.:

#\#CIF_2.0
# SPDX-License-Identifier: CC-BY-4.0

and by adding the _dictionary.licensing_SPDX dictionary attribute:

# ...
    _dictionary.ddl_conformance   4.2.0
    _dictionary.licensing_SPDX    CC-BY-4.0
# ...

Judging from the LICENSE.md file, the license you decided to go with is CC-BY-SA-4.0. Usually IUCr dictionaries go with CC-BY-4.0, but I am unsure if there would be any objection to using CC-BY-SA-4.0 instead. However, this is a separate discussion, so CC-BY-SA-4.0 would definitely work for now.

Dictionary version number

Given that the dictionaries are still in active development, it would be better to postfix their version numbers in _dictionary.version with -dev, e.g. 0.1.0-dev.

Changelog loop

To pass formal validation, dictionaries must end with the DICTIONARY_AUDIT loop that records the changes made between different version of the dictionaries. For the current dictionaries, I would suggest adding something like:

    loop_
      _dictionary_audit.version
      _dictionary_audit.date
      _dictionary_audit.revision
         0.1.0-dev                    2026-06-08 # Same date as the dictionary update date
;
       Work-in-progresss version of the initial dictionary release.
;