Added Castilla-La Mancha to list of DKAN sites

This region of Spain now has a DKAN open data portal located at https://datosabiertos.castillalamancha.es/

"Castilla–La Mancha is an autonomous community of Spain. It is mostly in this region where the story of the famous Spanish novel Don Quixote by Miguel de Cervantes is situated, due to which La Mancha is internationally well-known. Although La Mancha is a windswept, battered plateau, it remains a symbol of Spanish culture with its vineyards, sunflowers, mushrooms, olive plantations, windmills, Manchego cheese, and Don Quixote."

docs/introduction/dkan-sites.rst

@@ -159,6 +159,7 @@ Russia                                                                 http://da
 Moscow Region, Russia                                                  http://data.mosreg.ru
 Instituto Politécnico de Bragança, Portugal                            http://observatoriottm.ipb.pt
 Barcelona Provicial Diputation, Spain                                  https://dadesobertes.diba.cat/
+Castilla–La Mancha, Spain                                              https://datosabiertos.castillalamancha.es/
 Düsseldorf, Germany                                                    https://opendata.duesseldorf.de/
 The Republic of Cyprus                                                 http://www.data.gov.cy/
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