Rework handling of transitions

Make header and footer comply with the Helmholtz CD guidelines.

• Fix wrong positioning of green slider in header
• Transitions have been redesigned to be a bit more flexible
• It is possible to specify which transition is intended while including
• Added Path in SVG to also allow right side slider if required

Cherry-picked from https://gitlab.hzdr.de/hifis/software.hifis.net/-/commit/29b969b4b3702814342051961ea7ed61e8e57905