[Docs] Add Expo universal guide to documentation

docs/quick-start/expo-web-and-native.md

@@ -0,0 +1,85 @@
+---
+id: expo-web-and-native
+title: Expo Web and Native
+---
+
+# Quick Start for Expo targeting Web and Native
+
+To run Reactotron in an Expo app where you target both web and native platforms, you need to combine the "react-js" and "react-native" setup, and leverage the platform file extensions to load the right config for the current platform.
+
+If you are only targeting native platforms, or only targeting the web platform, you can use the [react-native](./react-native.md) or [react-js](./react-js.md) guides respectively.
+
+## Installing Reactotron.app
+
+Let’s [download the desktop app](https://github.com/infinitered/reactotron/releases?q=reactotron-app&expanded=true) to start. You can download for Linux, Windows, and Mac.
+
+Unzip & run.
+
+![Installing The App](./images/react-js/installing.jpg)
+
+## Configure Reactotron with your project
+
+#### **Step 1 - Add Reactotron as DEV dependency**
+
+Add Reactotron, in both react-native and react-js flavors, in your Expo project as a dev dependency.
+
+```
+npm i --save-dev reactotron-react-native reactotron-react-js
+```
+
+```
+yarn add reactotron-react-native reactotron-react-js -D
+```
+
+#### **Step 2 - Initialization**
+
+Create a file in your root folder `ReactotronConfig.native.js` and paste this:
+
+```js
+import Reactotron from "reactotron-react-native";
+
+Reactotron.configure() // controls connection & communication settings
+  .useReactNative() // add all built-in react native plugins
+  .connect(); // let's connect!
+```
+
+See the [react-native page](./react-native.md) if you want to customize Reactotron for React-native further.
+
+Then create another file in your root folder named `ReactotronConfig.web.js` and paste this:
+
+```js
+import Reactotron from "reactotron-react-js"
+
+Reactotron.configure() // we can use plugins here
+  .connect() // let's connect!
+```
+
+#### **Step 3 - Add Reactotron to your app**
+
+Finally, we import the configuration in the `app/_layout.js` file which is the lowest-level file that Expo Router gives us access to.
+
+After the imports:
+
+```js
+if (__DEV__) {
+  require("../ReactotronConfig"); // Or "../../ReactotronConfig" if you use a /src folder.
+}
+```
+
+Expo will load either the native or the web flavor of ReactotronConfig based on the platform it is running in. At this point, Reactotron is hooked up. **HOUSTON, WE HAVE A CONNECTION!**
+
+Refresh your app (or start it up with `expo start`) and have a look at Reactotron now. Do you see the `CONNECTION` line? Click that to expand.
+
+![We Have Contact](./images/react-native/first-connect.jpg)
+
+Go back to your app and refresh it 5 or 6 times. Now look.
+
+![Chatty](./images/react-native/spammy.jpg)
+
+## Troubleshooting
+
+**Android**: If you are using an Android device or an emulator run the following command to make sure it can connect to Reactotron:
+
+```
+adb reverse tcp:9090 tcp:9090
+```

docs/quick-start/react-native.md

@@ -5,6 +5,8 @@ title: react-native
 
 # Quick Start for React Native
 
+If you are using Expo *and* targeting *both* the native and web platforms, follow the [expo-web-and-native](./expo-web-and-native.md) guide instead.
+
 ## Installing Reactotron.app
 
 Let’s [download the desktop app](https://github.com/infinitered/reactotron/releases?q=reactotron-app&expanded=true) to start. You can download for Linux, Windows, and Mac.

docs/troubleshooting.md

@@ -52,3 +52,9 @@ and reload the app on your device.
 This only works on Android 5.x+.
 
 As of 1.1.4, the proper IP address is auto-discovered. Simply leave the `configure` as is.
+
+## Web
+
+If you are using Expo and open your app in a browser, having only integrated Reactotron for the native side, you will see some confusing errors.
+
+In this case you need to integrate Reactotron for *both* web and native by following this guide: [expo-web-and-native](./quick-start/expo-web-and-native.md)