(math/R-forcats) Updated 0.5.1 to 1.0.0

# forcats 1.0.0

## New features

* New `fct_na_value_to_level()` and `fct_na_level_to_value()` to convert
  NA values to NA levels and vice versa (#337).

## Minor improvement and bug fixes

* All functions now validate their inputs, giving more useful errors if you
  accidentally misspecify an input.

* `fct_collapse()` can now use `other_level = NA` (#291).

* `fct_count()` works with factors that contain `NA`s in levels.

* `fct_explicit_na()` is deprecated in favour of `fct_na_value_to_level()`.

* `fct_expand()` gains an `after` argument so that you can choose where
  the new levels are placed (#138).

* `fct_infreq()` gains the ability to weight by another variable using the `w`
  argument (#261).

* `fct_inorder()` now works when not all levels appear in the data (#262).

* `fct_lump_prop()` and friends now work correctly if you supply weights
  and have empty levels (#292).

* `fct_lump_n()` and `fct_lump_prop()` will now create an "Other" level even
  if it only consists of a single level. This makes them consistent with the
  other `fct_lump_*` functions (#274).

* `fct_other()` no longer generates a warning if no levels are replaced with
  other (#265).

* `fct_relevel()`, `fct_cross()`, and `fct_expand()` now error if you name the
  arguments in `...` since those names are ignored and your code probably
  doesn't do what you think it does (#319).

* `fct_reorder()` and `fct_reorder2()` now remove `NA` values in `.x` with a
  warning (like  `ggplot2::geom_point()` and friends). You can suppress the
  warning by setting `.na_rm = TRUE` (#315).

* `fct_reorder()` and `fct_reorder2()` gain a new `.default` argument that
  controls the placement of  empty levels (including levels that might become
  empty after removing missing values in `.x`) (#266).

* `fct_unique()` now captures implicit missing values if present (#293).

# forcats 0.5.2

* New `fct()` which works like `factor()` but errors if values of `x`
  are not included in the levels specification (#299)

* `first2()` and `last2()` now ignore missing values in both `x` and `y` (#303).

* Error messages are more informative.


(mef)