update readme with dune trick

README.md

@@ -36,7 +36,7 @@ $ opam install ancient
 $ export SHERLODOC_DB=/tmp/sherlodoc.ancient
 
 # index all odoc files generated by odig for your current switch:
-$ sherlodoc index $(find $OPAM_SWITCH_PREFIX/var/cache/odig/odoc -name '*.odocl')
+$ sherlodoc index $(find $OPAM_SWITCH_PREFIX/var/cache/odig/odoc -name '*.odocl' | grep -v __)
 ```
 
 Enjoy searching from the command-line or run the webserver:
@@ -70,7 +70,7 @@ Otherwise, manual integration with odoc requires to add to every call of `odoc h
 
 ```bash
 $ sherlodoc index --db=_build/default/_doc/_html/YOUR_LIB/db.js \
-    $(find _build/default/_doc/_odocls/YOUR_LIB -name '*.odocl')
+    $(find _build/default/_doc/_odocls/YOUR_LIB -name '*.odocl' | grep -v __)
 
 $ sherlodoc js > _build/default/_doc/_html/sherlodoc.js
 ```