README.adoc: document --output-format rf64 and some other options

Signed-off-by: Stefan Westerfeld <stefan@space.twc.de>

README.adoc

@@ -481,6 +481,24 @@ same. The watermarker has been designed and tested for stereo files,
 so the number of channels should really be `2`. This is also the
 default.
 
+== Other Command Line Options
+
+--output-format rf64::
+
+Regular wav files are limited to 4GB in size. By using this option,
+`audiowmark` will write RF64 wave files, which do not have this size limit.
+This is not the default because not all programs might be able to read RF64
+wave files.
+
+--q, --quiet::
+
+Disable all information messages generated by `audiomark`.
+
+--strict::
+
+This option will enable strict error checking, which may in some situations
+make `audiowmark` return an error, where it could continue.
+
 [[hls]]
 == HTTP Live Streaming