Improve remote documentation (#633)

Co-authored-by: Paulus Schoutsen <balloob@gmail.com>

docs/core/entity/remote.md

@@ -3,10 +3,6 @@ title: Remote Entity
 sidebar_label: Remote
 ---
 
-:::info Incomplete
-This entry is incomplete. Contribution welcome.
-:::
-
 ## Properties
 
 :::tip
@@ -16,4 +12,36 @@ Properties should always only return information from memory and not do I/O (lik
 | Name | Type | Default | Description
 | ---- | ---- | ------- | -----------
 
+## Supported Features
+
+| Constant | Description 
+| -------- | -----------
+| `SUPPORT_LEARN_COMMAND` | Entity allows learning commands from devices.
+
 ## Methods
+
+### Send Command
+
+```python
+class MyRemote(RemoteEntity):
+
+    def send_command(self, command: Iterable[str], **kwargs):
+        """Send commands to a device."""
+
+    async def async_send_command(self, command: Iterable[str], **kwargs):
+        """Send commands to a device."""
+```
+
+### Learn Command
+
+Only implement this method if the flag `SUPPORT_LEARN_COMMAND` is set.
+
+```python
+class MyRemote(RemoteEntity):
+
+    def learn_command(self, **kwargs):
+        """Learn a command from a device."""
+
+    async def async_learn_command(self, **kwargs):
+        """Learn a command from a device."""
+```