[Style guide] Update include section

[larshg]

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Update the include section, with the correct order of includes and add a comment about why its included.

[stale[bot]]

Marking this as stale due to 30 days of inactivity. It will be closed in 7 days if no further activity occurs.

[kunaltyagi]

I think this can be closed. I remember an addition to the style guide, but can't link the PR yet.

[larshg]

#4020 Solved this one :+1:

Well, somewhat. We are missing why are it included.

[kunaltyagi]

Could you expand a bit (or go ahead with a PR 😆 )?

[mvieth]

@larshg Do you have time/do you want to create a pull request to close this issue? You probably mean something like this?

#include <pcl/common/common.h> // for getMinMax3D
#include <pcl/pcl_macros.h> // for PCL_DEPRECATED