Improve unexpected tile count error

Do we even want to error early here? This isn't exactly fatal to reading
the image it is a only nuisance. It becomes crucial only when we are at
the point of reading all the tiles themselves.

src/error.rs

@@ -70,6 +70,9 @@ quick_error! {
         InconsistentSizesEncountered {
             display("inconsistent sizes encountered")
         }
+        IncorrectChunkCount {expected: u32, found: u32} {
+            display("incorrect number of chunk offsets encoded for the tile count of the image, expected {expected} but found {found}")
+        }
         InvalidDimensions(width: u32, height: u32) {
             display("invalid dimensions: {width}x{height}")
         }