Document build process

[Xiretza]

The only way to use this thing is to unpack release tarballs, how to get one of those from just the source tree is completely undocumented. This makes the software fairly obsolete, since the only one who can create a new usable version is @Secretmapper, and this hasn't happened in over two years.

[pakaoraki]

On linux:

Install NPM :

sudo dnf install npm 

# debian/ubuntu base should be : sudo apt install npm

Install yarn:
sudo npm install yarn -g

In combustion folder:

mkdir -p ../combustion-release

# Install dependencies:
yarn

# Execute build script:
./publish.sh

It should build files and move it to combustion-release folder.