Added changelog

.docs/changelog.md

dbrepo-search-service/clients/keycloak_client.py

dbrepo-search-service/clients/opensearch_client.py

dbrepo-search-service/omlib/__init__.py

dbrepo-search-service/omlib/constants.py

dbrepo-search-service/omlib/dimension.py

dbrepo-search-service/omlib/exceptions/__init__.py

dbrepo-search-service/omlib/exceptions/dimensionexception.py

...earch-service/omlib/exceptions/unitconversionexception.py

...-search-service/omlib/exceptions/unitidentityexception.py

dbrepo-search-service/omlib/measure.py

dbrepo-search-service/omlib/omconstants.py

dbrepo-search-service/omlib/rdf/__init__.py

dbrepo-search-service/omlib/rdf/om-2.0.rdf

dbrepo-search-service/omlib/scale.py

dbrepo-search-service/omlib/thing.py

dbrepo-search-service/omlib/unit.py