Add pwd command to stdlib (#9607)

Closes #9601

crates/nu-std/src/lib.rs

@@ -59,6 +59,7 @@ use std dirs [
     p
     dexit
 ]
+use std pwd
 "#
         );
 

crates/nu-std/std/mod.nu

@@ -286,3 +286,8 @@ It's been this long since (ansi green)Nushell(ansi reset)'s first commit:
 Startup Time: ($nu.startup-time)
 "
 }
+
+# Return the current working directory
+export def pwd [] {
+    $env.PWD
+}