feat: add dict.update til

python/dict-update-return-values.md

@@ -0,0 +1,5 @@
+# Python `dict.update` method returns `None`
+
+This is obvious in hindsight, but `dict.update` returns `None`, not the dictionary that's been updated in place.
+
+(This brief update brought to you by my attempting to use `dict.update` in a list comprehension after using JS object literal for too long.)