Tweak as_api_object documentation

I originally wrote this for lists, but it also works for character vectors, and may eventually expand to other objects like data frames. Thanks for catching the mismatch! Hopefully this fix makes as much sense as this can!

R/as.R

@@ -1,12 +1,13 @@
 #' Convert to a rapid-style object
 #'
-#' Convert a named list into an object with a rapid-style class.
+#' Convert an object into an object with a rapid-style class.
 #'
 #' @inheritParams rlang::args_dots_empty
 #' @inheritParams rlang::args_error_context
-#' @param x The named list to coerce. Must be empty or have names corresponding to
-#'   the parameter of the `target_class`, or names that can be coerced to those
-#'   names via [snakecase::to_snake_case()]. Extra names are ignored.
+#' @param x The object to coerce. Must be empty, or be a named list or character
+#'   vector having names corresponding to the parameter of the `target_class`,
+#'   or names that can be coerced to those names via
+#'   [snakecase::to_snake_case()]. Extra names are ignored.
 #' @param target_class The S7 class to which the object should be converted.
 #' @param alternate_names Character vector (optional). An optional named
 #'   character vector, where the names are the names as they might appear in