Corrected gitlab ssh link

See merge request !6

 - corrected link to the unicado-package

- Corrected the File structure plaintext box

- Changed emojis from "\emoji wink" to 
- Changed note/warning syntax from @note/warning to:

!!! note
        Text.

- Added pictures to text

Maybe this works when committed, but currently the preview cannot properly display:
- @note/@warning
- \emoji

And the preview displays written marks for cross-references ({#introduction}).

New layout

See merge request !4

Add a merge request documentation

See merge request !3