Add preprocessing section to 'Airplane Crashes and Fatalities'

[MYCIN-AI-Club]

The contributor is expected to preprocess the data which involves cleaning of the data, checking for null values and outliners and similar tasks.
This issue is expected to be delivered within 2 days of assignment to the contributor.

[Shivang2003]

please assign me the task

[MYCIN-AI-Club]

Great! @Shivang2003 ! I am assigning you the task!