Add env.nu file for environment config (#5099)

* Add env.nu file for environment config

* Add missing flag

* Add $nu.env-path variable

Prints `env.nu` path

* Add example of adding entries to PATH

crates/nu-engine/src/eval.rs

@@ -1142,6 +1142,7 @@ pub fn eval_variable(
 
             if let Some(mut config_path) = nu_path::config_dir() {
                 config_path.push("nushell");
+                let mut env_config_path = config_path.clone();
 
                 let mut history_path = config_path.clone();
 
@@ -1160,6 +1161,14 @@ pub fn eval_variable(
                     val: config_path.to_string_lossy().to_string(),
                     span,
                 });
+
+                env_config_path.push("env.nu");
+
+                output_cols.push("env-path".into());
+                output_vals.push(Value::String {
+                    val: env_config_path.to_string_lossy().to_string(),
+                    span,
+                });
             }
 
             #[cfg(feature = "plugin")]