`drop` is used for removing the last row. Passing a number allows dropping N rows.
Here we introduce the same logic for dropping columns instead.
You can certainly remove columns by using `reject`, however, there could be cases
where we are interested in removing columns from tables that contain, say, a big
number of columns. Using `reject` becomes impractical, especially when you don't
care about the column names that could either be known or not known when exploring
tables.
```
> echo [[lib, extension]; [nu-core, rs] [rake, rb]]
─────────┬───────────
lib │ extension
─────────┼───────────
nu-core │ rs
rake │ rb
─────────┴───────────
```
```
> echo [[lib, extension]; [nu-core, rs] [rake, rb]] | drop column
─────────
lib
─────────
nu-core
rake
─────────
```
