Add day1 test

src/day01.rs

@@ -78,3 +78,13 @@ fn parse_digit(s: &str) -> u32 {
         _ => s.parse().unwrap(),
     }
 }
+
+mod tests {
+    use super::find_digits_part2;
+
+    #[test]
+    fn twone() {
+        assert_eq!(find_digits_part2("twone"), 21);
+        assert_eq!(find_digits_part2("8oneightakljsdf"), 88);
+    }
+}