Use anim_opts = anim_options() instead of NULL

Leads to better documentation where it is easier to understand how to use the anim_opts parameter

R/animate_tidyr.R

 #'   # if you want to have a less detailed animation, you can also use
 #'   animate_gather(wide, "person", "sales", -year, export = "gif", detailed = FALSE)
 #' }
-animate_gather <- function(w, key, value, ..., export = "gif", detailed = TRUE, anim_opts = NULL) {
+animate_gather <- function(w, key, value, ..., export = "gif", detailed = TRUE, anim_opts = anim_options()) {
   anim_opts <- default_anim_opts("gather", anim_opts)
   lhs <- w
   rhs <- tidyr::gather(w, !!key, !!value, ...)
 #'   # if you want to have a less detailed animation, you can also use
 #'   animate_spread(long, key = "person", value = "sales", export = "gif", detailed = FALSE)
 #' }
-animate_spread <- function(l, key, value, export = "gif", detailed = TRUE, ..., anim_opts = NULL) {
+animate_spread <- function(l, key, value, export = "gif", detailed = TRUE, ..., anim_opts = anim_options()) {
   anim_opts <- default_anim_opts("spread", anim_opts)
 
   lhs <- l

man/animate_gather.Rd

 \title{Animates the gather function}
 \usage{
 animate_gather(w, key, value, ..., export = "gif", detailed = TRUE,
-  anim_opts = NULL)
+  anim_opts = anim_options())
 }
 \arguments{
 \item{w}{a data_frame in the wide format}

man/animate_spread.Rd

 \title{Animates the spread function}
 \usage{
 animate_spread(l, key, value, export = "gif", detailed = TRUE, ...,
-  anim_opts = NULL)
+  anim_opts = anim_options())
 }
 \arguments{
 \item{l}{a data_frame in the long/tidy format}