Make iOS bundle id agnostic (#486)

## Description

Made changes to describe how to build the example app

## Motivation and Context

bundleIdentifier on iOS was tied to fishjam and wouldn't build on real
device for people outside of fishjam org

## Documentation impact

- [ ] Documentation update required
- [ ] Documentation updated [in another PR](_)
- [X] No documentation update required

## Types of changes

- [X] Bug fix (non-breaking change which fixes an issue)
- [ ] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing
functionality to
      not work as expected)

---------

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
Co-authored-by: Miłosz Filimowski <MiloszFilimowski@users.noreply.github.com>

Author: 3 people

examples/mobile-client/fishjam-chat/README.md

@@ -36,6 +36,18 @@ yarn
 yarn build
 ```
 
+> [!IMPORTANT]
+> Before prebuilding, replace all occurrences of `io.fishjam.example.fishjamchat` in `app.json` with your own bundle identifier:
+>
+> - **iOS bundle identifier** — `expo.ios.bundleIdentifier`
+> - **Android package name** — `expo.android.package`
+>
+> For example, if your bundle ID is `com.yourcompany.yourapp`:
+>
+> - iOS & Android: `com.yourcompany.yourapp`
+> - ScreenBroadcastExtension: `com.yourcompany.yourapp.ScreenBroadcastExtension`
+> - App group: `group.com.yourcompany.yourapp`
+
 3. Prebuild native files in example directory:
 
 ```sh
@@ -56,10 +68,13 @@ yarn android
 ## Development
 
 1. Whenever you make changes in the `packages` directory, make sure to build the app in the root directory (not in `examples/mobile-client/fishjam-chat`). This ensures that all related workspaces are also built:
+
 ```sh
 yarn build
 ```
+
 2. Linter (run in the root directory):
+
 ```sh
 yarn lint
 ```