docs: Documentation and minor changes

src/cli.rs

@@ -21,7 +21,7 @@ pub enum Commands {
         #[arg(short='a', long, default_value = "UN")]
         initials: String,
 
-        #[arg(short='a', long, default_value = "TRUEVISION-XFILE")]
+        #[arg(short='s', long, default_value = "TRUEVISION-XFILE")]
         signature: String,
     },
 

src/encoder.rs

@@ -7,8 +7,8 @@ use std::io::{BufWriter, Write};
 use std::path::Path;
 
 pub fn encode(input: &Path, output: &Path, initials: &str, signature: &str, origin: u8) -> Result<()> {
-    if signature.len() > 15 {
-        return Err(GfxError::Format("Signature longer than 15 bytes!".into()));
+    if signature.len() > 16 {
+        return Err(GfxError::Format("Signature longer than 16 bytes!".into()));
     }
 
     let img = image::open(input)?;