Document speed_count for fans and the utility

docs/core/entity/fan.md

@@ -17,6 +17,7 @@ Properties should always only return information from memory and not do I/O (lik
 | is_on | boolean | None |Return true if the entity is on |
 | oscillating | boolean | None | Return true if the fan is oscillating |
 | percentage | int | None | Return the current speed percentage. Must be a value between 0 (off) and 100 |
+| speed_count | int | 100 | The number of speeds the fan supports |
 | supported_features | int | 0 | Flag supported features |
 | preset_mode | str | None | Return the current preset_mode. One of the values in preset_modes. |
 | preset_modes | list | None | Get the list of available preset_modes. This is an arbitrary list of str and should not contain any speeds. |
@@ -103,18 +104,42 @@ ORDERED_NAMED_FAN_SPEEDS = ["one", "two", "three", "four", "five", "six"]  # off
 percentage = ordered_list_item_to_percentage(ORDERED_NAMED_FAN_SPEEDS, "three")
 
 named_speed = percentage_to_ordered_list_item(ORDERED_NAMED_FAN_SPEEDS, 23)
+
+...
+
+    @property
+    def percentage(self) -> Optional[int]:
+        """Return the current speed percentage."""
+        return ordered_list_item_to_percentage(ORDERED_NAMED_FAN_SPEEDS, current_speed)
+
+    @property
+    def speed_count(self) -> Optional[int]:
+        """Return the number of speeds the fan supports."""
+        return len(ORDERED_NAMED_FAN_SPEEDS)
 ```
 
 If the device has a numeric range of speeds:
 
 ```python
-from homeassistant.util.percentage import ranged_value_to_percentage, percentage_to_ranged_value
+from homeassistant.util.percentage import int_states_in_range, ranged_value_to_percentage, percentage_to_ranged_value
 
 SPEED_RANGE = (1, 255)  # off is not included
 
 percentage = ranged_value_to_percentage(SPEED_RANGE, 127)
 
 value_in_range = math.ceil(percentage_to_ranged_value(SPEED_RANGE, 50))
+
+...
+
+    @property
+    def percentage(self) -> Optional[int]:
+        """Return the current speed percentage."""
+        return ranged_value_to_percentage(SPEED_RANGE, current_speed)
+
+    @property
+    def speed_count(self) -> Optional[int]:
+        """Return the number of speeds the fan supports."""
+        return int_states_in_range(SPEED_RANGE)
 ```
 :::