Add a release.sh script and indicate what needs to be done to finish it

I'm working on adding a script to generate the release.json file necessary to add to i2p.newsxml for your updates, as you can see I've got the first and last part ready, but there is a section in the middle which may depends on your preferred tools for each of these tasks and more importantly, where those tools are. I don't know for sure what the equivalents of

• java -cp $I2P/lib/i2p.jar:$I2P/lib/i2psnark.jar org.klomp.snark.Storage -for generating the torrent
• java -cp $I2P/lib/i2p.jar net.i2p.crypto.SU3File -for generating the .su3 file

will be in a jpackage i2p install on a Mac, or whether it would be easier to use something else instead(in i2p.firefox I'm using mktorrent and the su3 tools from the reseed server). Once we work out these details release.sh be ready to generate releases. i2p.newsxml is already adapted and will pick up on the release.json file as soon as it's present.