Update Data Preparation section with de-identification changes, anchors and links

[vkalokyri]

No description provided.

[Palollo]

Hi @vkalokyri,
I see the "target-blank" functionality (i.e. open in new tab) is not supported in markdown and target attribute in <a> is not either recognized and so mantained in the final output. So not working at the end. I'm going to resolve the conflicts and merge the rest of changes. Is that ok for you?

[vkalokyri]

Hi @Palollo,
You are right. It was working when I tested it locally but GitBook explicitly states that external links open in the same tab by default for accessibility reasons. Feel free to merge the rest of the changes. However, I think we should still find a way to open links in a new tab as requested by the users (it seems that there is a global site-wide setting that allows this).