This package offers content NodeTypes for two, three and four column layouts in a very simple manner. Please consider this a example implementation - you probably want to implement your own.
This package renders a layout div, like <div class="container columns-25-75">[content]</div> for a two column layout with a left 25% column and on the right a 75% column. You need to bring your own CSS, which implements the layout.
If you want to contribute to Neos, please have a look at https://github.com/neos/neos-development-collection - it is the repository used for development and all pull requests should go into it.