daily job running mobile example on real devices (#8216)

# Objective

- Test mobile example on real devices

## Solution

- Use [BrowserStack](https://www.browserstack.com) to have access to
[real
devices](https://www.browserstack.com/list-of-browsers-and-platforms/app_automate)
- [App Automate](https://www.browserstack.com/app-automate) to run the
example
- [App Percy](https://www.browserstack.com/app-percy) to compare the
screenshot
- Added a daily/manual CI job that will build for iOS and Android, send
the apps to BrowserStack, run the app on one iOS device and one Android
device, capture a screenshot, send it for visual validation, and archive
it in the GitHub action

Example run: https://github.com/mockersf/bevy/actions/runs/4521883534

They currently have a bug with the settings to view snapshots, they
should be public. I'll raise it to them, and if they don't fix it in
time it's possible to work around for everyone to view the results
through their API.

@cart to get this to work, you'll need
- to set up an account on BrowserStack
- add the secrets `BROWSERSTACK_USERNAME` and `BROWSERSTACK_ACCESS_KEY`
to the Bevy repo
- create a project in Percy
- add the secret `PERCY_TOKEN` to the Bevy repo and modify the project
name line 122 in the `Daily.yml` file

Author: mockersf

.github/start-mobile-example/.gitignore

@@ -0,0 +1,5 @@
+node_modules/
+/test-results/
+/playwright-report/
+/playwright/.cache/
+screenshot.png

.github/start-mobile-example/mobile.conf.js

@@ -0,0 +1,35 @@
+exports.config = {
+    user: process.env.BROWSERSTACK_USERNAME,
+    key: process.env.BROWSERSTACK_ACCESS_KEY,
+
+    updateJob: false,
+    specs: [
+        './specs/screenshot.js'
+    ],
+    exclude: [],
+
+    capabilities: [{
+        project: "Bevy Example",
+        build: 'Bevy Example Runner',
+        name: 'run_example',
+        device: process.env.DEVICE || 'Samsung Galaxy S23',
+        os_version: process.env.OS_VERSION || "13.0",
+        app: process.env.BROWSERSTACK_APP_ID,
+        'browserstack.debug': true,
+        orientation: 'LANDSCAPE'
+    }],
+
+    logLevel: 'info',
+    coloredLogs: true,
+    screenshotPath: './screenshots/',
+    baseUrl: '',
+    waitforTimeout: 10000,
+    connectionRetryTimeout: 90000,
+    connectionRetryCount: 3,
+
+    framework: 'mocha',
+    mochaOpts: {
+        ui: 'bdd',
+        timeout: 20000
+    }
+};