LudvigOlsen/groupdata2: groupdata2 1.2.0

Adds Zenodo DOI for easier citation.

Adds lifecycle badges to function documentation.

Adds argument handle_na to differs_from_previous() and find_starts().

Bug fix: In grouping functions with method l_starts and n = "auto", NAs are now replaced by a unique value before finding group starts. E.g. c(1,1,1,2,2,NA,NA,4,4) yields 4 groups.

More explicit: the data argument in fold() and participant takes a data frame, not a vector.

Possibly breaking change: Adds checkmate input checks. Improves error messages but also restricts behavior.

Adds xpectr as suggested package. Doubles number of unit tests.