refactor(viewer): rename app to "mm" and improve navigation features

src/main.rs

@@ -23,6 +23,7 @@ pub fn main() -> Result<()> {
 fn walker(input: impl AsRef<Path>) -> Vec<PathBuf> {
     let mut tb = ignore::types::TypesBuilder::new();
     tb.add("image", "*.jpg").expect("Failed to add image type");
+    tb.add("image", "*.png").expect("Failed to add image type");
     ignore::WalkBuilder::new(input)
         .types(
             tb.select("image")