Example with notifee foreground notification to keep the app alive in background

[dprevost-LMI]

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• Explain the motivation for making this change.
• Provide a test plan demonstrating that the code is solid.
• Match the code formatting of the rest of the codebase.
• Target the main branch, NOT a "stable" branch.

Motivation (required)

I enhanced the example project to give a complete, working example of the Notifee foreground service, keeping the app alive in the background when taking a picture or video with the camera.

What existing problem does the pull request solve?
Solve the problem where the app is killed in the background while using the camera, and when exiting the camera, your app gets restarted and lands on the home page.

Test Plan (required)

Using the simulator on different Android versions, I validated that we were seeing the foreground notification.
This is also where I found that Android 8 and 9 required camera permission, even if it was not in the manifest. , So I provide another example of requesting camera permission.

[dprevost-LMI]

@gabrieldonadel or @cipolleschi, you seem to commit often. Does the above add value for this project else I will just close it