include 4.20 in automatic builds

Author: Roberto De Ioris

tools/release_win64.py

@@ -5,7 +5,7 @@
 import shutil
 import zipfile
 
-UE_VERSIONS = ['4.15', '4.16', '4.17', '4.18', '4.19']
+UE_VERSIONS = ['4.15', '4.16', '4.17', '4.18', '4.19', '4.20']
 PYTHON_VERSIONS = ["C:/Program Files/Python36", "C:/Program Files/Python37", "C:/Python27"]
 
 RELEASE_DIR = sys.argv[1].rstrip('/')