graphics/input: Move getevent README.md to index.rst documentation.

Replace README.md with index.rst format documentation for getevent
tool to follow NuttX documentation conventions. The rst file should
be placed under Documentation/applications/testing/getevent/ in the
NuttX main repository.

Signed-off-by: liuhongchao <liuhongchao@xiaomi.com>

Author: HongChao6

graphics/input/getevent/README.md

@@ -0,0 +1,56 @@
+====================================
+``getevent`` Input Event Monitor Tool
+====================================
+
+The ``getevent`` utility monitors input events from mouse, touch, and keyboard
+devices in real-time. It supports automatic input device detection in ``/dev``
+and command-line device path specification.
+
+Features
+--------
+
+- Mouse event monitoring (clicks, movement, wheel)
+- Multi-touch event capture (coordinates, pressure, timestamps)
+- Keyboard key press detection (key codes, event types)
+- Automatic input device detection in ``/dev``
+- Non-blocking I/O with 500ms timeout
+- Resource-safe memory management
+
+Build Configuration
+-------------------
+
+Enable in NuttX configuration:
+
+- ``CONFIG_GRAPHICS_INPUT_GETEVENT`` -- Enable getevent tool.
+- ``CONFIG_GRAPHICS_INPUT_GETEVENT_STACKSIZE`` -- Stack size for getevent task.
+- ``CONFIG_GRAPHICS_INPUT_GETEVENT_PRIORITY`` -- Priority of getevent task.
+- ``CONFIG_GRAPHICS_INPUT_GETEVENT_DETAIL_INFO`` -- Enable detailed information
+  in getevent output, such as touch width, height, and pressure.
+
+Usage
+-----
+
+.. code:: bash
+
+   # Auto-detect all input devices
+   getevent
+
+   # Monitor specific mouse device
+   getevent -m /dev/mouse0
+
+   # Monitor specific touch device
+   getevent -t /dev/input0
+
+   # Monitor specific keyboard
+   getevent -k /dev/kbd0
+
+   # Combine multiple devices
+   getevent -m /dev/mouse0 -t /dev/input0
+
+Press ``Ctrl+C`` to safely terminate the monitoring process.
+
+Requirements
+------------
+
+- NuttX input subsystem support must be enabled.
+- Kernel syslog output must be configured for event logging.