fix: Add temporary main function to lib.rs

src/lib.rs

@@ -0,0 +1,12 @@
+#[allow(dead_code)]
+fn main() {
+    println!("Hello, world!");
+}
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn it_works() {
+        assert_eq!(2 + 2, 4);
+    }
+}