doc: add NODE_DEBUG_NATIVE to API docs

This commit adds the missing environment variable
NODE_DEBUG_NATIVE to the CLI API docs.

PR-URL: nodejs#24383
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Sam Roberts <vieuxtech@gmail.com>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Ouyang Yadong <oyydoibh@gmail.com>
Reviewed-By: Weijia Wang <starkwang@126.com>
Reviewed-By: Franziska Hinkelmann <franziska.hinkelmann@gmail.com>
Reviewed-By: Vse Mozhet Byt <vsemozhetbyt@gmail.com>
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>

Author: cjihrig

doc/api/cli.md

@@ -539,6 +539,10 @@ added: v0.1.32
 
 `','`-separated list of core modules that should print debug information.
 
+### `NODE_DEBUG_NATIVE=module[,…]`
+
+`','`-separated list of core C++ modules that should print debug information.
+
 ### `NODE_DISABLE_COLORS=1`
 <!-- YAML
 added: v0.3.0