Doc comments, format string inlining, long literal separators

- Doc comments on DriveSession, find_drives, all Error variants, Result type
- 24 format! strings inlined (clippy pedantic)
- 25 long hex literals with separators (0xFFFFFFFF → 0xFFFF_FFFF)
- README install example updated to 0.8

src/mux/mkvstream.rs

@@ -512,7 +512,7 @@ fn parse_track(r: &mut (impl Read + Seek), size: u64) -> io::Result<Option<crate
         "S_VOBSUB" => Codec::DvdSub,
         _ => Codec::Unknown(0),
     };
-    let res = format!("{}p", ph);
+    let res = format!("{ph}p");
     let chs: String = match ch {
         8 => "7.1",
         6 => "5.1",