docs: Updated docs around total export sensor

Author: BottlecapDave

_docs/entities/electricity.md

@@ -482,7 +482,7 @@ The total consumption reported by the meter for all time. This will try and upda
     This will only be available if you have specified you have an [Octopus Home Mini](../setup/account.md#home-mini). Do not set unless you have one.
 
 !!! info
-    Not all meters provide this information. In these scenarios, this sensor will report zero.
+    Not all meters provide this information. In these scenarios, this sensor will report zero or unknown.
 
 !!! note
     This is [disabled by default](../faq.md#there-are-entities-that-are-disabled-why-are-they-disabled-and-how-do-i-enable-them).
@@ -493,6 +493,7 @@ The total export reported by the meter for all time. This will try and update ev
 |-----------|------|-------------|
 | `mpan` | `string` | The mpan for the associated meter |
 | `serial_number` | `string` | The serial for the associated meter |
+| `is_export` | `boolean` | Determines if the meter exports energy rather than imports |
 | `is_smart_meter` | `boolean` | Determines if the meter is considered smart by Octopus Energy |
 
 ### Current Accumulative Cost