Improve INSPIRE keywords

- [ ] Extend the INSPIRE schemas of ckan-pycsw (`ckan `& `pygeometa`) to generate at least keywords from the following thesauri:
   - INSPIRE Themes
   - Spatial Scope
   - GEMET
   - Service Type (if `dcat_type `is `service`)

- [ ] Additionally, all text values without thesaurus are incorporated as keywords.

https://github.com/mjanez/ckan-pycsw/tree/main/ckan2pycsw/schemas