fix: base64.py 'Incorrect padding' error

Update python implementation of 'atob' to properly reflect behaviour of JS 'atob'.

Author: Ciarands

python/pythonmonkey/builtin_modules/base64.py

@@ -8,7 +8,10 @@
 
 
 def atob(b64):
-  return str(base64.standard_b64decode(b64), 'latin1')
+  # Workaround for pythons 'Incorrect padding' error when base64 decoding, see: 
+  # https://stackoverflow.com/questions/2941995/python-ignore-incorrect-padding-error-when-base64-decoding
+  append = b"==" if isinstance(b64, bytes) else "=="
+  return str(base64.standard_b64decode(b64 + append), 'latin1')
 
 
 def btoa(data):