Mention print in the echo help text (nushell#12436)

# Description
Edits the `echo` help text to mention the `print` command.

---------

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

crates/nu-cmd-lang/src/core_commands/echo.rs

@@ -20,8 +20,10 @@ impl Command for Echo {
     }
 
     fn extra_usage(&self) -> &str {
-        r#"When given no arguments, it returns an empty string. When given one argument,
-it returns it. Otherwise, it returns a list of the arguments. There is usually
+        r#"Unlike `print`, which prints unstructured text to stdout, `echo` is like an
+identity function and simply returns its arguments. When given no arguments,
+it returns an empty string. When given one argument, it returns it as a
+nushell value. Otherwise, it returns a list of the arguments. There is usually
 little reason to use this over just writing the values as-is."#
     }