add examples with .. and / to path join (#10620)

related to
-
https://discord.com/channels/601130461678272522/615329862395101194/1159484770468773990

# Description
because the following might not be trivial
```nushell
> "/foo/bar" | path join "/" "baz"
/baz
```
i thought adding a few examples to the `path join` command might help
😇

# User-Facing Changes
two new examples in `help path join` one with `..` and the other with
`/` 👍

# Tests + Formatting
the examples have `result`s so that they are checked.

# After Submitting

---------

Co-authored-by: Darren Schroeder <343840+fdncred@users.noreply.github.com>

crates/nu-command/src/path/join.rs

@@ -90,6 +90,17 @@ the output of 'path parse' and 'path split' subcommands."#
                 example: r"'C:\Users\viking' | path join spams this_spam.txt",
                 result: Some(Value::test_string(r"C:\Users\viking\spams\this_spam.txt")),
             },
+            Example {
+                description: "Use relative paths, e.g. '..' will go up one directory",
+                example: r"'C:\Users\viking' | path join .. folder",
+                result: Some(Value::test_string(r"C:\Users\viking\..\folder")),
+            },
+            Example {
+                description:
+                    "Use absolute paths, e.g. '/' will bring you to the top level directory",
+                example: r"'C:\Users\viking' | path join / folder",
+                result: Some(Value::test_string(r"C:/folder")),
+            },
             Example {
                 description: "Join a list of parts into a path",
                 example: r"[ 'C:' '\' 'Users' 'viking' 'spam.txt' ] | path join",
@@ -124,6 +135,17 @@ the output of 'path parse' and 'path split' subcommands."#
                 example: r"'/home/viking' | path join spams this_spam.txt",
                 result: Some(Value::test_string(r"/home/viking/spams/this_spam.txt")),
             },
+            Example {
+                description: "Use relative paths, e.g. '..' will go up one directory",
+                example: r"'/home/viking' | path join .. folder",
+                result: Some(Value::test_string(r"/home/viking/../folder")),
+            },
+            Example {
+                description:
+                    "Use absolute paths, e.g. '/' will bring you to the top level directory",
+                example: r"'/home/viking' | path join / folder",
+                result: Some(Value::test_string(r"/folder")),
+            },
             Example {
                 description: "Join a list of parts into a path",
                 example: r"[ '/' 'home' 'viking' 'spam.txt' ] | path join",