Update HttpResponse.getBodyAsJSONObject to support "application/[something]+json" Content-Type headers

[Yavor Vasilev]

Trying to parse a JWK set with

JWKSet retrievedJWKSet = JWKSet.parse(httpResponse.getBodyAsJSONObject());

currently produces

com.nimbusds.oauth2.sdk.ParseException: The HTTP Content-Type header must be application/json, received application/jwk-set+json

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[Yavor Vasilev]

Done: 20dbc7c88a151ff2fd107b882ae667793b5ca1fd

(for JSONArray and JWT as well)