doc: add section about using npx with permission model

doc/api/permissions.md

@@ -126,6 +126,21 @@ does not exist, the wildcard will not be added, and access will be limited to
 yet, make sure to explicitly include the wildcard:
 `/my-path/folder-do-not-exist/*`.
 
+#### Enabling Permission Model with npx
+
+If you're using `npx` to execute a Node.js script, you can enable the Permission
+Model by using the `--node-options` flag.
+
+```bash
+npx --node-options="--permission --allow-fs-read=./" your-script
+```
+
+This argument will set the `NODE_OPTIONS` environment variable to all
+Node.js processes spawned by `npx` (without affecting `npx` itself!).
+
+Any arguments you would normally pass directly to `node`
+(such as `--allow-*` flags) can also be passed through `--node-options`.
+
 #### Permission Model constraints
 
 There are constraints you need to know before using this system: