Add a :dedup or :uniq command #15297
Description
It would be nice to have a convenient way to remove duplicates after sorting lines, similar to | sort | uniq in shell. Some other uniq options may also be useful, such as -d/--repeated or -i/--ignore-case https://man7.org/linux/man-pages/man1/uniq.1.html.
Alternatively this could be spelled as :sort -u (also supported by the sort shell command).