Update setup.py and CHANGELOG.md for 0.3.20 release

Author: davidplowman

CHANGELOG.md

@@ -6,6 +6,20 @@
 
 ### Changed
 
+## 0.3.20 Beta Release 19
+
+### Added
+
+* Initial support for Hailo AI devices, including some examples.
+* IMX708 helper class so that the sensor HDR mode can be set with Python.
+
+### Changed
+
+* Improved handling of timeouts when cameras stop responding, including a mechanism for a complete
+  reset if requests stop being returned.
+* Platform checking more robust.
+* Add missing flush parameter to captured_request() (for use with context manager).
+
 ## 0.3.19 Beta Release 18
 
 ### Added

setup.py

@@ -11,7 +11,7 @@
 
 setup(
     name='picamera2',
-    version='0.3.19',
+    version='0.3.20',
     description='The libcamera-based Python interface to Raspberry Pi cameras, based on the original Picamera library',
     long_description=long_description,
     long_description_content_type='text/markdown',