scheme attribute for media:credit and media:rating

[ksridhar]

in https://github.com/amagimedia/metadata/blob/main/amgrss_schemas/amgrss_xpaths_description.csv as per specification at https://www.rssboard.org/media-rss#media-credit and https://www.rssboard.org/media-rss#media-rating. The master example at https://github.com/amagimedia/metadata/blob/dfa0453e3b7e65ae59364a243c03965ab30ebcee/amgrss_schemas/amgrss_master.xml#L59 and https://github.com/amagimedia/metadata/blob/dfa0453e3b7e65ae59364a243c03965ab30ebcee/amgrss_schemas/amgrss_master.xml#L16 mention them (i.e. the scheme attribute)

[shashi-banger]

Add: /rss/channel/item[]/media:credit[]/@role -> Preferred label of amg:role

scheme is fixed so no need to add as attribute scheme value http://www.ebu.ch/metadata/ontologies/skos/ebu_RoleCodeCS.rdf

[shashi-banger]

For rating also scheme is fixed to http://www.ebu.ch/metadata/ontologies/skos/ebu_ParentalGuidanceCodeCS.rdf