Fix inconsistencies in mimetype icons between light/dark versions
This is necessary preparation for the automatic generation of the breeze dark theme. These are mostly just copy/pasted from one theme into another to remove inconsistencies. Significantly changing the looks of individual icons is outside of the scope of this patch because it would take too long if I had to really touch up every icon.
I already know this works, so I'll land this later on 2020-07-12 if nobody brings up any issues.
cc: @teams/vdg
Edited by Noah Davis