feat(docs): migrate from .md to .rst (#4129)

docs/widgets/switch.rst

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+Switch (lv_switch)
+==================
+
+Overview
+********
+
+The Switch looks like a little slider and can be used to turn something
+on and off.
+
+Parts and Styles
+****************
+
+-  :cpp:enumerator:`LV_PART_MAIN` The background of the switch uses all the typical
+   background style properties. ``padding`` makes the indicator smaller
+   in the respective direction.
+-  :cpp:enumerator:`LV_PART_INDICATOR` The indicator that shows the current state of
+   the switch. Also uses all the typical background style properties.
+-  :cpp:enumerator:`LV_PART_KNOB` A rectangle (or circle) drawn at left or right side
+   of the indicator. Also uses all the typical background properties to
+   describe the knob(s). By default, the knob is square (with an
+   optional corner radius) with side length equal to the smaller side of
+   the slider. The knob can be made larger with the ``padding`` values.
+   Padding values can be asymmetric too.
+
+Usage
+*****
+
+Change state
+------------
+
+The switch uses the standard :cpp:enumerator:`LV_STATE_CHECKED` state.
+
+To get the current state of the switch (with ``true`` being on), use
+:cpp:expr:`lv_obj_has_state(obj, LV_STATE_CHECKED)`.
+
+Call :cpp:expr:`lv_obj_add_state(obj, LV_STATE_CHECKED)` to turn it on, or
+:cpp:expr:`lv_obj_clear_state(obj, LV_STATE_CHECKED)` to turn it off.
+
+Events
+******
+
+-  :cpp:enumerator:`LV_EVENT_VALUE_CHANGED` Sent when the switch changes state.
+
+See the events of the `Base object </widgets/obj>`__ too.
+
+Learn more about :ref:`events`.
+
+Keys
+****
+
+-  ``LV_KEY_UP/RIGHT`` Turns on the slider
+-  ``LV_KEY_DOWN/LEFT`` Turns off the slider
+-  :cpp:enumerator:`LV_KEY_ENTER` Toggles the switch
+
+Learn more about :ref:`indev_keys`.
+
+Example
+*******
+
+.. include:: ../examples/widgets/switch/index.rst
+
+API
+***