Fix: Enable Tablet Mode Auto-Rotation on Arch Linux

[tynen]

Of course. Here is a pull request description based on the guide you created. You can use this as a template for submitting your changes.

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Fix: Enable Tablet Mode Auto-Rotation on Arch Linux

Problem

Automatic screen rotation does not work out of the box on many Arch Linux installations (and its derivatives) for two primary reasons:

1. The iio-sensor-proxy package, which is required to read accelerometer data, is not installed by default.
2. The version of iio-sensor-proxy available in some repositories (version 3.7) has a known [upstream bug](https://gitlab.freedesktop.org/hadess/iio-sensor-proxy/-/issues/411) that prevents it from correctly processing sensor data due to a faulty udev rule.

This leaves users without a functional tablet mode experience.

Solution

This PR adds a new guide that provides a clear, step-by-step solution for Arch Linux users to enable automatic screen rotation. The guide instructs users to:

1. Install the necessary package: sudo pacman -S iio-sensor-proxy
2. Apply a udev workaround: A sed command is used to comment out the problematic iio-buffer-accel line in the udev rules, forcing the system to use a working method to poll the sensor.
3. Restart the relevant services to apply the changes immediately.

This approach resolves the issue completely and restores the expected auto-rotation functionality.

How to Test

1. Follow the steps outlined in the new "Arch Linux Tablet Mode Setup" guide.
2. Run monitor-sensor --accel after completing the steps.
3. Confirm that the output includes the line === Has accelerometer (orientation: normal).
4. Physically rotate the device to confirm the screen orientation changes accordingly.