typo fixes all over the place

found and semi-manually replaced by using:
 codespell -L mut -L crate -i 3 -w

Mostly in comments, but also email notification and two occurrences
of misspelled  'reserved' struct member, which where not used and
cargo build did not complain about the change, soo ...

Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>

src/tape/helpers/snapshot_reader.rs

@@ -85,7 +85,7 @@ impl SnapshotReader {
         Ok(file)
     }
 
-    /// Retunrs an iterator for all used chunks.
+    /// Returns an iterator for all used chunks.
     pub fn chunk_iterator(&self) -> Result<SnapshotChunkIterator, Error> {
         SnapshotChunkIterator::new(&self)
     }