Keep current fold in table of Contant when moving between file

[Yuval91]

Keep the current table of content fold when moving between files

For a file with some hierarchy of sections (with title1, title2 etc.), the table of content on the sidebar allows to fold sections and keep only some unfolded.
But when moving between files and coming back to them, the sidebar-table-of-content unfold everything again. This makes the navigation in the document harder, and you have to refold everything. It is especially annoying in bigger files.

Please make it so, that last "folds-state" is kept when moving between files.