Add select integration (#969)

Co-authored-by: Martin Hjelmare <marhje52@gmail.com>

docs/core/entity/select.md

@@ -0,0 +1,38 @@
+---
+title: Select Entity
+sidebar_label: Select
+---
+
+A `select` is an entity that allows the user to select an option from a list of limited options provided by the integration. Derive entity platforms from [`homeassistant.components.select.SelectEntity`](https://github.com/home-assistant/core/blob/dev/homeassistant/components/select/__init__.py)
+
+This entity should only be used in cases there is no better fitting option available.
+For example, a bulb can have user selectable light effects. While that could be done using this `select` entity, it should really be part of the `light` entity, which already supports light effects.
+
+## Properties
+
+> Properties should always only return information from memory and not do I/O (like network requests). Implement `update()` or `async_update()` to fetch data.
+
+| Name | Type | Default | Description
+| ---- | ---- | ------- | -----------
+| current_option | str | None | The current select option
+| options | list | **Required** | A list of available options as strings
+
+Other properties that are common to all entities such as `icon`, `unit_of_measurement`, `name` etc are also applicable.
+
+## Methods
+
+### Select option
+
+Called when the user or automation wants to change the current selected option.
+
+```python
+class MySelect(SelectEntity):
+    # Implement one of these methods.
+
+    def select_option(self, option: str) -> None:
+        """Change the selected option."""
+
+    async def async_select_option(self, option: str) -> None:
+        """Change the selected option."""
+
+```

sidebars.js

@@ -161,6 +161,7 @@ module.exports = {
       "core/entity/media-player",
       "core/entity/number",
       "core/entity/remote",
+      "core/entity/select",
       "core/entity/sensor",
       "core/entity/switch",
       "core/entity/vacuum",