Add docs/logging.md to ex_doc extras configuration

The logging.md file existed but was missing from the ex_doc configuration,
causing documentation build warnings about missing file references.

Author: benoitc

rebar.config

@@ -41,6 +41,7 @@
         <<"docs/context-affinity.md">>,
         <<"docs/streaming.md">>,
         <<"docs/memory.md">>,
+        <<"docs/logging.md">>,
         <<"docs/scalability.md">>,
         <<"docs/threading.md">>,
         <<"docs/asyncio.md">>,
@@ -53,7 +54,8 @@
             <<"docs/type-conversion.md">>,
             <<"docs/context-affinity.md">>,
             <<"docs/streaming.md">>,
-            <<"docs/memory.md">>
+            <<"docs/memory.md">>,
+            <<"docs/logging.md">>
         ]},
         {<<"Advanced">>, [
             <<"docs/scalability.md">>,