change ManifestError export

It's now exported from the main crate directly.

src/lib.rs

@@ -2,7 +2,7 @@
 #![deny(missing_debug_implementations)]
 
 pub mod entries;
-pub mod error;
+mod error;
 mod file;
 mod parser;
 
@@ -12,6 +12,7 @@ mod generated {
     include!(concat!(env!("OUT_DIR"), "/schema_generated.rs"));
 }
 
+pub use crate::error::ManifestError;
 pub use crate::file::File;
 pub use crate::parser::header::Header;
 pub use crate::parser::manifest::ManifestData;