Add hugo bib to README

[maltevogl]

Follwing the readme to setup a local Hugo will give an error because of the missing hugo library dependeny. This should be added.

To reproduce:

• Clone the repository e.g. git clone git@github.com:dh-tech/dh-tech.github.io.git
• install hugo
• Run hugo server

gives

Error: error building site: process: readAndProcessContent: "path/github/dh-tech.github.io/content/literature.md:5:3": failed to extract shortcode: template for shortcode "bibliography" not found

Solved by checking out the submodule, in my case git submodule update --init --recursive