Add README and sdbus-c++ tutorial as additional pages in doxydocs (#153)

Co-authored-by: Craig Spannring <craig.spannring@milnxpd001.mti.local>
Co-authored-by: Stanislav Angelovič <angelovic.s@gmail.com>

docs/CMakeLists.txt

@@ -12,6 +12,10 @@ if(BUILD_DOXYGEN_DOC)
             COMMENT "Generating API documentation with Doxygen"
             VERBATIM)
 
+        # workaround bug https://github.com/doxygen/doxygen/pull/6787
+        add_custom_command(TARGET doc POST_BUILD
+          COMMAND ${CMAKE_COMMAND} -E copy ${CMAKE_CURRENT_LIST_DIR}/sdbus-c++-class-diagram.png ${CMAKE_CURRENT_BINARY_DIR}/html/.)
+        
         install(DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}/html DESTINATION ${CMAKE_INSTALL_DOCDIR} OPTIONAL)
     else()
         message(WARNING "Documentation enabled, but Doxygen cannot be found")

docs/Doxyfile.in

@@ -790,7 +790,9 @@ WARN_LOGFILE           =
 # spaces. See also FILE_PATTERNS and EXTENSION_MAPPING
 # Note: If this tag is empty the current directory is searched.
 
-INPUT                  = "@CMAKE_CURRENT_SOURCE_DIR@/../include"
+INPUT                  = "@CMAKE_CURRENT_SOURCE_DIR@/../include" \
+                          @CMAKE_CURRENT_SOURCE_DIR@/../README.md \
+                          @CMAKE_CURRENT_SOURCE_DIR@/using-sdbus-c++.md
 
 # 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
@@ -982,7 +984,7 @@ FILTER_SOURCE_PATTERNS =
 # (index.html). This can be useful if you have a project on for instance GitHub
 # and want to reuse the introduction page also for the doxygen output.
 
-USE_MDFILE_AS_MAINPAGE =
+USE_MDFILE_AS_MAINPAGE = README.md
 
 #---------------------------------------------------------------------------
 # Configuration options related to source browsing