First steps towards time-evolution methods for MPS

[claudius-hubig]

Hi,

these commits contain the first batch of content of the time-evolution for MPS review. Apart from adding the content itself, I've also made small tweaks to the generate.jl, bibtex.jl and README.md files to

• recognise multi-line \cite{}
• strip leading whitespace from citation labels
• recognise \begin{align}
• pass --unsafe to cmark
• explain the steps to setup a local generator in the README.md
• link to the DOI of a reference if it does not have a URL

Please feel free to pick any commits you like, please also let me know if the content of the TEBD page is good as-is or whether I should spend more time adapting it to the website format. If the content is ok as-is, I will add the other methods and experiments in the next few days.

[emstoudenmire]

Thanks for the excellent PR! I really appreciate having this, and I think it's already up to the quality I'm hoping for the site. The figures in particular look really good and it's no problem if their style looks slightly different from my figures.

Thanks also for the improvements to the site generator. I'm actually working on a new generator (mostly done) that I will use for both this site and itensor.org. It's a more modular design with "plugins" controlling features such as Bibtex support, and it's more customizable, allowing the choice of different Markdown parsers for example. (And I may make my own "Latex lite" parser too as we discussed.)