docs: update citation file

inst/CITATION

@@ -1,14 +1,17 @@
 citHeader("To cite cfda, use:")
 
-citEntry(
-  entry    = "Article",
-  title    = "Categorical Functional Data Analysis. The cfda R Package",
-  author   = personList(as.person("Cristian Preda"), as.person("Quentin Grimonprez"), as.person("Vincent Vandewalle")),
-  journal  = "Mathematics",
-  year     = "2021",
-  volume   = "9",
-  number   = "23",
-  url      = "https://www.mdpi.com/2227-7390/9/23/3074",
-  doi      = "10.3390/math9233074",
-  textVersion = paste("Preda C, Grimonprez Q, Vandewalle V. Categorical Functional Data Analysis. The cfda R Package. Mathematics. 2021; 9(23):3074. https://doi.org/10.3390/math9233074")
+bibentry(
+  bibtype = "Article",
+  title = "Categorical Functional Data Analysis. The cfda R Package",
+  author = c(person("Cristian Preda"), person("Quentin Grimonprez"), person("Vincent Vandewalle")),
+  journal = "Mathematics",
+  year = "2021",
+  volume = "9",
+  number = "23",
+  url = "https://www.mdpi.com/2227-7390/9/23/3074",
+  doi = "10.3390/math9233074",
+  textVersion = paste(
+    "Preda C, Grimonprez Q, Vandewalle V. Categorical Functional Data Analysis.",
+    "The cfda R Package. Mathematics. 2021; 9(23):3074. https://doi.org/10.3390/math9233074"
+  )
 )