Make cea608.js a proper NPM package

[tobbee]

cea608.js is used in dash.js, but it is not obvious where the code comes from.

Making cea608.js a proper NPM package would facilitate version handling and inclusion of the code, as well as usage in other environments.

I was looking into doing this some years ago, but it was I got stuck and thought there wouldn't be many updates. There have been some bugs found, though, so it is still worth doing. Help in the process would be appreciated.