Add a user agent to all requests
Wikidata started to block requests without a proper user agent, so we need to add one:
https://gitlab.com/dlr-dw/semanticFacets/-/blob/master/src/util/ThrottledRequests.js#L54
headers: {
'Content-type': 'application/x-www-form-urlencoded',
'Accept': 'application/sparql-results+json',
'User-Agent': 'semanticFacets',
},