Add 'every' command to select (or skip) every nth row (#1992)

* Add 'every' command

* Add --skip option to 'every' command

This option skips instead of selects every nth row

* Fix descriptions for 'every' command

* Add docummentation for 'every' command

* Check actual filenames in 'every' command tests

crates/nu-cli/tests/commands/mod.rs

@@ -10,6 +10,7 @@ mod default;
 mod drop;
 mod each;
 mod enter;
+mod every;
 mod first;
 mod format;
 mod get;