deleted all placeholder texts and added placeholder side bars

wiki/pages/attributions.html

wiki/pages/contribution.html

wiki/pages/description.html

wiki/pages/education.html

wiki/pages/engineering.html

wiki/pages/entrepreneurship.html

wiki/pages/experiments.html

wiki/pages/hardware.html

wiki/pages/human-practices.html

wiki/pages/inclusivity.html

wiki/pages/measurement.html

wiki/pages/model.html

wiki/pages/notebook.html

wiki/pages/plant.html

wiki/pages/results.html

wiki/pages/safety.html

wiki/pages/software.html

wiki/pages/sustainable.html

wiki/pages/team.html