Alias CfgNode as CN

[Rizhiy]

In the example CfgNode is imported as CN.
In my code, I also do the same, since it saves a bit of space.

Unfortunately, my IDE (PyCharm) is not able to automatically recognise this alias and I have to manually import CfgNode every time, which becomes tedious after a while if you use it a lot.

I suggest adding CN as a proper alias, so that IDE can detect it.

Name clash

So far I haven't seen any major variables in other packages named CN, the only conflict is https://pypi.org/project/cn/#description, but it appears to be empty and dead.