add registeration url

data/events.json

@@ -63,6 +63,7 @@
             "venue": "Norrlands Nation, Uppsala",
             "organisers": "Clinical Microbiology, Laboratory Medicine, Uppsala University Hospital",
             "event_url": "https://nordicantiviral.se/",
+            "registration_url": "https://nordicantiviral.se/registration/",
             "description": "The program for the 7th Nordic Conference of Antiviral Treatment Strategies and Drug Resistance (previously the Nordic Conference of HIV and Hepatitis Drug Resistance and Treatment Strategies) is completed. This one-day meeting is aimed to attract MD´s and researchers from the Nordic countries, whose activities involve treatment of HIV, hepatitis B/C, SARS-CoV-2 and other virus infection, as well as antiviral drug resistance. Renowned international and national scientist has been invited to present current findings in the fields."
         },
         {