feat: rewrite programming-challenges CLI (#3)

templates/solution/rust/solution.rs

@@ -0,0 +1,8 @@
+use std::io::{self, BufRead};
+
+fn main() {
+  let stdin = io::stdin();
+  for line in stdin.lock().lines() {
+    println!("Hello, {}!", line.unwrap());
+  }
+}