feat: move vec exercises into their own folder

exercises/vecs/vecs1.rs

@@ -0,0 +1,25 @@
+// vecs1.rs
+// Your task is to create a `Vec` which holds the exact same elements
+// as in the array `a`.
+// Make me compile and pass the test!
+// Execute `rustlings hint vecs1` or use the `hint` watch subcommand for a hint.
+
+// I AM NOT DONE
+
+fn array_and_vec() -> ([i32; 4], Vec<i32>) {
+    let a = [10, 20, 30, 40]; // a plain array
+    let v = // TODO: declare your vector here with the macro for vectors
+
+    (a, v)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_array_and_vec_similarity() {
+        let (a, v) = array_and_vec();
+        assert_eq!(a, v[..]);
+    }
+}