Adding Tensorflow to graph_encoding

Author: brianjjones

phases/ephemeral/docs.md

@@ -1326,6 +1326,8 @@ Alignment: 1
 - <a href="#graph_encoding.openvino" name="graph_encoding.openvino"></a> `openvino`
 TODO document buffer order
 
+- <a href="#graph_encoding.tensorflow" name="graph_encoding.tensorflow"></a> `tensorflow`
+
 ## <a href="#execution_target" name="execution_target"></a> `execution_target`: `Variant`
 Define where the graph should be executed.
 

phases/ephemeral/witx/wasi_ephemeral_nn.witx

@@ -81,6 +81,7 @@
   (enum (@witx tag u8)
     ;;; TODO document buffer order
     $openvino
+    $tensorflow
   )
 )