vctrs 0.3.5

• New experimental vec_fill_missing() for filling in missing values with
  the previous or following value. It is similar to tidyr::fill(), but
  also works with data frames and has an additional max_fill argument to
  limit the number of sequential missing values to fill.

• New vec_unrep() to compress a vector with repeated values. It is very
  similar to run length encoding, and works nicely alongside vec_rep_each()
  as a way to invert the compression.

• vec_cbind() with only empty data frames now preserves the common size of
  the inputs in the result (#1281).

• vec_c() now correctly returns a named result with named empty inputs
  (#1263).

• vctrs has been relicensed as MIT (#1259).

• Functions that make comparisons within a single vector, such as
  vec_unique(), or between two vectors, such as vec_match(), now
  convert all character input to UTF-8 before making comparisons (#1246).

• New vec_identify_runs() which returns a vector of identifiers for the
  elements of x that indicate which run of repeated values they fall in
  (#1081).

• Fixed an encoding translation bug with lists containing data frames which
  have columns where vec_size() is different from the low level
  Rf_length() (#1233).