Handle CORS with screepsmod-cors (for README)

There is a neat mod for handling CORS. Just install it and cross-origin-requests are allowed 😄
https://github.com/ScreepsMods/screepsmod-cors

You may update the section about "How to use" in the README 

Thanks for this nice client 👍 
Just found screeps last week and if I like it, I'll contribute to this repo 😃 

PS: Did you abandon this project or are there any plans going forward?