doc: add process.debugPort to doc/api/process.md

Fixes: #18639

PR-URL: #18716
Refs: #18639
Reviewed-By: Colin Ihrig <[email protected]>
Reviewed-By: Luigi Pinca <[email protected]>
Reviewed-By: James M Snell <[email protected]>
Reviewed-By: Matheus Marchini <[email protected]>
Reviewed-By: Benjamin Gruenbaum <[email protected]>
Reviewed-By: Tobias Nießen <[email protected]>

Author: flickz

doc/api/process.md

@@ -621,7 +621,17 @@ process.
 ```js
 console.log(`Current directory: ${process.cwd()}`);
 ```
+## process.debugPort
+<!-- YAML
+added: v0.7.2
+-->
+* {number}
 
+The port used by Node.js's debugger when enabled.
+
+```js
+process.debugPort = 5858;
+```
 ## process.disconnect()
 <!-- YAML
 added: v0.7.2