Algorand Dev Portal article has issues fixed in this codebase

[excalq]

First, thank you immensely for the excellent tutorial on Algorand.org, as a web3 (EVM) game developer learning Algorand, it's educational and fun.

I wanted to give a heads up that the tutorial, Simple NPC game interactions using a stateful contract and atomic transfers, has a number of minor mistakes, which are fixed in this repo's code, but haven't been applied to the article yet.

1. Missing definition of is_creator (line 10) of contract.py

2. Bytes("damage") should be Bytes("injure") on Line 40 of contract.py

3. Makefile references to $(ALGO_(DATA) and $(ALGO__DATA) (should be $(ALGO_DATA))

4. Makefiles also require tabs, not spaces (This may not be fixable in the article, depending on their CMS)

5. goal node start -d $(ALGO_PVTNET_DATA) is a useful command to add after the private node install. (I'm a complete AlgoN00b!)

6. creatorAddress and differentAddress needing some figuring out. goal account new was useful for creating the differentAddress.
   It may be helpful to give commands to create and fund a second account:

   goal account new
   goal account list
   goal clerk send -a 200000 -f $CREATOR_ACCOUNT -t $NEW_ACCOUNT 
   

   I hope this helps! Thanks again!