Strip custom sections in wasm-prune (#150)

* strip custom sections

* line width

src/optimizer.rs

@@ -330,6 +330,10 @@ pub fn optimize(
 		}
 	}
 
+	// Also drop all custom sections
+	module.sections_mut()
+		.retain(|section| if let elements::Section::Custom(_) = section { false } else { true });
+
 	Ok(())
 }