Add pedestrian bridge example

Add the pedestrian bridge example in the folder example/pedestrian_bridge. Put all the related things that are necessary into this folder. Ideally, it should contain

• a notebook daaad_pipeline_pedestrian_bridge.ipynb defining the entire pipeline from data set definition to evaluation
• additional scripts that define the importer function
• the dataset used, stored with git-lfs

See examples/semiramis/ for inspiration, it should have a similar structure.