S3 method for the + operator to join two summary tables created by
summarise_by. Tables must have identical .wider_by attributes
to be joined.
# S3 method for eam_summarise_by_tbl
+(e1, e2)A joined data frame with class "eam_summarise_by_tbl", preserving the .wider_by attribute from the input tables
First eam_summarise_by_tbl object
Second eam_summarise_by_tbl object