rename markdown files

tinyusb.Doxyfile

@@ -744,10 +744,10 @@ WARN_LOGFILE           =
 # Note: If this tag is empty the current directory is searched.
 
 INPUT                  = tinyusb/doxygen/group_def.txt \
-                         readme.md \
+                         readme.markdown \
                          tinyusb \
                          boards \
-                         tests/readme.markdown
+                         tests/readme.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
@@ -925,7 +925,7 @@ 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 = readme.md
+USE_MDFILE_AS_MAINPAGE = readme.markdown
 
 #---------------------------------------------------------------------------
 # Configuration options related to source browsing