Documentation for Home Assistant Number (#3942)

Co-authored-by: Jesse Hills <3060199+jesserockz@users.noreply.github.com>

components/number/home_assistant.rst

@@ -0,0 +1,36 @@
+Home Assistant Number
+=====================
+
+.. seo::
+        :description: Instructions for setting up Home Assistant numbers with ESPHome.
+        :image: description.svg
+
+The ``homeassistant`` number platform allows you to create a number that is synchronized
+with Home Assistant. Min, Max and Step are not configurable for this platform because they are taken from the Home Assistant entity.
+
+.. code-block:: yaml
+
+    # Example configuration entry
+    number:
+      - platform: homeassistant
+        id: my_ha_number
+        entity_id: number.my_number
+
+Configuration variables:
+------------------------
+
+- **entity_id** (**Required**, string): The Home Assistant entity ID of the number to synchronize with.
+- All other options from :ref:`Number <config-number>`.
+
+``number.set`` Action
+---------------------
+
+You can also set the number for the Home Assistant number from elsewhere in your YAML file
+with the :ref:`number-set_action`.
+
+See Also
+--------
+
+- :ref:`automation`
+- :apiref:`homeassistant/number/homeassistant_number.h`
+- :ghedit:`Edit`