feat(react-native): Document Expo plugin options for sentry.options.json generation

docs/platforms/react-native/manual-setup/app-start-error-capture.mdx

@@ -107,9 +107,7 @@ class AppDelegate: UIResponder, UIApplicationDelegate {
 
 ## Expo Setup
 
-If you're using Expo, you can enable native initialization using the Expo plugin. First, create a `sentry.options.json` file in your project root (same location as your `app.json`) [as above](#configuration-file).
-
-Add the `useNativeInit` option to your Expo plugin configuration:
+If you're using Expo, you can enable native initialization using the Expo plugin. Add the `useNativeInit` option and your SDK options to the plugin configuration:
 
 ```json {filename:app.json}
 {
@@ -118,21 +116,33 @@ Add the `useNativeInit` option to your Expo plugin configuration:
       [
         "@sentry/react-native/expo",
         {
-          "useNativeInit": true
+          "useNativeInit": true,
+          "options": {
+            "dsn": "https://key@example.io/value",
+            "environment": "production",
+            "tracesSampleRate": 1.0
+          }
         }
       ]
     ]
   }
 }
 ```
 
+The plugin generates a `sentry.options.json` file from the `options` property during `expo prebuild`. If a `sentry.options.json` file already exists in your project root, the plugin options are merged into it (plugin options take precedence).
+
 If you need to use environment variables or dynamic configuration, you can use `app.config.js` with the `withSentry()` wrapper instead of the array form in `app.json`:
 
 ```javascript {filename:app.config.js}
 import { withSentry } from "@sentry/react-native/expo";
 
 export default withSentry(config, {
   useNativeInit: true,
+  options: {
+    dsn: "https://key@example.io/value",
+    environment: "production",
+    tracesSampleRate: 1.0,
+  },
 });
 ```
 
@@ -142,25 +152,9 @@ When `useNativeInit` is set to `true`, the Expo plugin automatically:
 
 ### Setting the Environment
 
-You can set the `environment` for native initialization using the Expo plugin prop or the `SENTRY_ENVIRONMENT` environment variable. The plugin writes the value into `sentry.options.json` during `expo prebuild`.
+You can set the `environment` using the plugin `options` property as shown above, or using the `SENTRY_ENVIRONMENT` environment variable. The environment variable takes precedence over the plugin option.
 
-```json {filename:app.json}
-{
-  "expo": {
-    "plugins": [
-      [
-        "@sentry/react-native/expo",
-        {
-          "useNativeInit": true,
-          "environment": "staging"
-        }
-      ]
-    ]
-  }
-}
-```
-
-For per-environment builds with EAS Build, set `SENTRY_ENVIRONMENT` in your build profiles instead:
+For per-environment builds with EAS Build, set `SENTRY_ENVIRONMENT` in your build profiles:
 
 ```json {filename:eas.json}
 {
@@ -174,5 +168,3 @@ For per-environment builds with EAS Build, set `SENTRY_ENVIRONMENT` in your buil
   }
 }
 ```
-
-The plugin prop takes precedence over the environment variable.