[Documentation:System] added documentation for preserving files

[hyeenaa]

created documentation for #12158

[Farhanxikram]

It looks like fine documentation. It thoroughly explains the process of preserving changes on a system-reinstallation :)

[Rkoester47]

The information added to the documentation looks useful to me, good job! My only concern is that I think the sentences you've added should be capitalized to match the formatting of the rest of the documentation.

[hyeenaa]

The information added to the documentation looks useful to me, good job! My only concern is that I think the sentences you've added should be capitalized to match the formatting of the rest of the documentation.

Thank you for that catch! It is updated so that the formatting is kept uniform.