fix sln parsing form vs2019 (#679)

emsdk.py

diff --git a/emsdk.py b/emsdk.py
index f344830..6d30c56 100644
--- a/emsdk.py
+++ b/emsdk.py
@@ -917,7 +917,7 @@
 
 def get_generator_for_sln_file(sln_file):
   contents = open(sln_file, 'r').read()
-  if '# Visual Studio 16' in contents:  # VS2019
+  if '# Visual Studio 16' in contents or '# Visual Studio Version 16' in contents:  # VS2019
     return 'Visual Studio 16'
   if '# Visual Studio 15' in contents:  # VS2017
     return 'Visual Studio 15'