Added test citation to test-citiatons.csv only found on springer, tha…

…t cites a doi

inst/testdata/test-citations.csv

@@ -6,3 +6,4 @@ pub_id,lead_author_surname,year,title,dataset_id_as_cited,dataone_pid,source
 10.1186/s40665-016-0017-0,Radville,2016,Root phenology in an Arctic shrub-graminoid community: the effects of long-term warming and herbivore exclusion,https://doi.org/10.18739/A23H1N,arctic-data.6185.2,springer
 10.5194/essd-11-1957-2019,Broadman,2019,"An Arctic watershed observatory at Lake Peters, Alaska: Weather-glacier-river-lake system data for 2015-2018",https://doi.org/10.18739/a2zs2kc8c,10.18739/A2ZS2KC8C,scopus
 10.1029/2018JG004528,Koch,2018,Ice Wedge Degradation and Stabilization Impact Water Budgets and Nutrient Cycling in Arctic Trough Ponds,https://arcticdata.io/catalog/#view/doi:10.18739/A29K97,10.18739/A29K97,xdd
+10.1007/s13280-019-01295-7,Schwoerer,2020,Hitchhikers on floats to Arctic freshwater: Private aviation and recreation loss from aquatic invasion,https://doi.org/10.18739/A2M32N95V,10.18739/A2M32N95V,springer