Bump rebar3_ex_doc from 0.2.18 to 0.2.23

Author: paulo-ferraz-oliveira

rebar.config

@@ -28,7 +28,7 @@
 {project_plugins, [
   {covertool, "2.0.6"},
   {rebar3_lint, "3.2.5"}
-  {rebar3_ex_doc, "0.2.18"}
+  {rebar3_ex_doc, "0.2.23"}
 ]}.
 {ex_doc, [
     {extras, [