docs: add --node-externals build command to the config page (#439)

Author: sommeeeer

docs/pages/config.mdx

@@ -1,7 +1,9 @@
 ### Build Arguments
 
-There is a single build argument that you can pass to the `open-next build` command: 
+There is two build arguments that you can pass to the `open-next build` command:
+
 - `--config-path` - This is the path to the configuration file that you want to use. By default, it will look for `open-next.config.ts` in the current working directory. This needs to be relative to the current working directory.
+- `--node-externals` - You can configure externals for the esbuild compilation of the `open-next.config.ts` file (i.e `--node-externals @aws-sdk/*,open-next/dist/queue/*`)
 
 ### Configuration File
 
@@ -13,4 +15,4 @@ If you want to take a look at some simple configuration examples, you can check
 
 For more advanced use cases, you can check [how to implement custom overrides](/config/custom_overrides).
 
-If you want to look at a full example, you can check [the full example](/config/full_example).
+If you want to look at a full example, you can check [the full example](/config/full_example).