Check meta-schema

[tschmidtb51]

Our meta-schema currently only references the core and format-assertion vocabulary. We might need to add:

    "https://json-schema.org/draft/2020-12/vocab/applicator": true,
    "https://json-schema.org/draft/2020-12/vocab/unevaluated": true,
    "https://json-schema.org/draft/2020-12/vocab/validation": true,
    "https://json-schema.org/draft/2020-12/vocab/meta-data": true,
    "https://json-schema.org/draft/2020-12/vocab/content": true

We need to verify that. (Implementation of #813 might be incomplete.)

[bernhardreiter]

The current JSON Schema specification (2020-12) says

8.1.2.2. Non-inheritability of vocabularies

Note that the processing restrictions on "$vocabulary" mean that meta-schemas that reference other meta-schemas using "$ref" or similar keywords do not automatically inherit the vocabulary declarations of those other meta-schemas. All such declarations must be repeated in the root of each schema document intended for use as a meta-schema.

This suggests that https://github.com/oasis-tcs/csaf/blob/8de9bc2de4e765b51951986373e7bd1eab13fc56/csaf_2.1/json_schema/meta.json potentially misses some wanted vocabulary declarations as they are not inherited from https://json-schema.org/draft/2020-12/schema .