Attempts to add a command that checks if nushell is running with admin priveleges (#5712)

* attempts to add is-admin command

* fmt and clippy

* fmt

* Update is_admin.rs

* typos

* typo in example

crates/nu-command/src/default_context.rs

@@ -382,6 +382,7 @@ pub fn create_default_context(cwd: impl AsRef<Path>) -> EngineState {
         // Experimental
         bind_command! {
             ViewSource,
+            IsAdmin,
         };
 
         // Deprecated