[DOC] schema language versus specification language

[VisLab]

1. Does schema language == specification language?
   The website title for https://schema-language.readthedocs.io/en/latest/description.html is Specification Language. It might be helpful to have a consistent terminology for this.

2. The Namespaces doc says:

The beginning of the file must begin with a comment that starts with ‘nwb-schema-language’ followed by a space and the version string of the specification language used by this namespace, e.g., nwb-schema-language 2.2.0. Files without this comment are assumed to be defined using nwb-schema-language 2.1.0.

The template does not generate this comment and running create_extension_spec writes over the comment in xxx.namespaces.yaml. Is there a way to set the generation of this comment or another way to do this? @rly