FUSE: write tutorial doc

It will be useful to have a tutorial document showing how to use the FUSE file system with concrete interesting examples. E.g.:

• here is how to mount the archive and cat the content of an interesting file (sched.c in the kernel? the doom example? an Apollo 11 file? etc.)
• here's how to ls an interesting directory
• here's how to sloccount on an old release
• here's how to navigate a commit history
• etc.

let's start collecting here in followups some examples as a starting point (cc: @haltode, who has collected some already)

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Migrated from T2676 (view on Phabricator)