Sub:add temp failsafe page

Author: Hwurzburg

sub/source/docs/internal-temperature-failsafe.rst

@@ -0,0 +1,10 @@
+.. _internal-temperature-failsafe:
+
+=============================
+Internal Temperature Failsafe
+=============================
+Sub can use the barometer normally included with an autopilot to determine if the temperature inside the sub has increased too much. The trigger temperature is set by :ref:`FS_TEMP_MAX<FS_TEMP_MAX>`. If it is exceeded, then the following actions is taken as set by the value of the :ref:`FS_TEMP_ENABLE<FS_PRESS_ENABLE>` parameter:
+
+-  **Disabled** (Value 0) will disable the failsafe entirely.
+-  **Warn Only** (Value 1) will send a GCS warning message.
+