Updated README and fixed run-server.sh to clear folder before moving new files in

[Kryptoxic]

Updated README to specify downloading the Node.js version instead of the Linux version for the Foundry ZIP file.

[Kryptoxic]

After @Fronix 's bug report, I debugged and realised that my changes assumed that the resources/app was empty. I added a step to delete all files in the folder before moving the extracted files into said folder.

[Kryptoxic]

@Fronix I've just built and pushed a new docker image on my account. Feel free to pull that and try it out to see if it works. Remember to backup your data/directory as well if you have any data on your server just in case anything goes wrong.

image: cryptoxic/fvtt-docker:latest