AAudio: Add Doxygen configuration file

Added files:
Doxyfile.orig - corresponds to default Doxyfile for Doxygen version 1.8.6
Doxyfile - Doxyfile.orig modified for Oboe

Other related changes:
Corrected Doxygen comment typo in AAudio.h
Added instructions in README on how to use Doxygen

Bug: 35255705
Test: run doxygen in same directory as Doxyfile
Change-Id: I9f431474a17b9e87b8e75347a50f561344204d83
diff --git a/media/libaaudio/include/aaudio/AAudio.h b/media/libaaudio/include/aaudio/AAudio.h
index 6987955..dad5285 100644
--- a/media/libaaudio/include/aaudio/AAudio.h
+++ b/media/libaaudio/include/aaudio/AAudio.h
@@ -405,7 +405,7 @@
  *
  * @param stream A stream created using AAudioStreamBuilder_openStream().
  * @param periodNanoseconds the estimated period at which the audio thread will need to wake up
- * @param startRoutine your thread entry point
+ * @param threadProc your thread entry point
  * @param arg an argument that will be passed to your thread entry point
  * @return AAUDIO_OK or a negative error.
  */