Fix Citation Date showing not the right date

[nkurtys]

While working on issue #93 I founds following issue:
The Date generated in the citation of the Knowledge Base page as well the "created at" part seem to not line up with the actual dates edited.

[nkurtys]

• the date seems to always be the current date
• the date works as intended when used on a local machine

[nkurtys]

There are two solutions:

• add fetch-depth: 0 to fetch the entire history, but that can be slow depending on repo history.
• concatenating git fetch --unshallow && onto the build command

Source: gjtorikian/jekyll-last-modified-at#69

[nkurtys]

fetch-depth: 0 fixed it on github pages but not on the nfdi subdomain