docs: add documentation on minimizing lambda bundle

Author: khuezy

README.md

@@ -633,6 +633,25 @@ await build({
 
 This feature is currently **experimental** and needs to be opted into. It can significantly decrease the server function's cold start time. Once it is thoroughly tested and its stability is confirmed, it will be enabled by default.
 
+#### Reducing Bundle Size
+
+Next will incorrectly trace dev dependencies to be included in the output `node_modules`, which will significantly increase the lambda bundle. For example, the @swc/core-\* binary is ~33MB!
+
+Add this to your next.config.js to help minimize the lambda bundle size:
+
+```typescript
+    outputFileTracingExcludes: {
+      '*': [
+        '**@swc/core**',
+        '**esbuild**',
+        '**webpack**',
+        '**uglify**',
+      ],
+    },
+```
+
+NOTE: NextJS currently doesn't expose an environmental variable to set this so `open-next` cannot programmatically set this like it does for `mode` and `outputFileTracingRoot`
+
 #### Reusing same bucket for asset and cache
 
 Typically, asset files are uploaded to the root of the bucket. However, you might want to store them in a subfolder of the bucket, for instance, when: