Adding timeline theme

[Lucas-C]

I designed a simple 2-columns layout for Pelican, could it be added here as a submodule please ?

https://github.com/Lucas-C/pelican-theme-timeline

[rask004]

One way to do this:

1. Fork the pelican-themes repo.
2. Clone your fork to a local directory.
3. Use the "git submodule" command to add your theme repo as a submodule.
4. Commit changes to master branch of your fork, then submit a pull request to merge the fork into pelican-themes.

Contributors will review your pull request when they are able to. This may take a while depending on workloads.