fix doxy display (#514)

### What problem were solved in this pull request?

Issue Number: close #xxx

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Author: nautaa

docs/Doxyfile

@@ -943,7 +943,7 @@ WARN_LOGFILE           =
 # spaces. See also FILE_PATTERNS and EXTENSION_MAPPING
 # Note: If this tag is empty the current directory is searched.
 
-INPUT                  = src/observer
+INPUT                  = src/
 
 # This tag can be used to specify the character encoding of the source files
 # that doxygen parses. Internally doxygen uses the UTF-8 encoding. Doxygen uses