Update changelog for 1.4.0

README.rst

@@ -175,6 +175,13 @@ Q: When I try to send a packet to the loopback address on Windows, I get "[WinEr
 Changelog
 =========
 
+v1.4.0 - Dec 21, 2023
+*********************
+* multicast_expert now has Github Actions CI thanks to Victor Tang's contribution!  It is now automatically tested on Mac, Linux, and Windows.
+* Add ``enable_external_loopback`` option on tx and rx sockets, which can be used to turn on multicast loopback for non-loopback interfaces.  Note that this option has to be set on both the Tx and Rx sockets in order to work correctly on all platforms.
+* Fix bug which prevented opening IPv6 multicast Tx sockets on Linux in some situations
+* Fix mypy type checker error on non-Windows platforms due to use of ctypes Windows functionality.
+
 v1.3.0 - Oct 20, 2023
 *********************
 * Replace ``blocking`` arg to McastRxSocket with ``timeout``, which allows you to set an integer timeout in the constructor. The old argument is still supported but is marked as legacy.