We should use relative links for images in docusaurus documents
Currently, the links in .md documents that refer to other documents or images are all absolute, e.g.
![eSSIF-Lab Architecture](https://essif-lab.pages.grnet.gr/essif-lab/images/eSSIF-Lab-Architecture.png)
However in the README.md it says: "Images must be put inside static
and referred to with their relative urls."