Add a test for unchecked-index crate

Author: qryxip

tests/unchecked-index.rs

@@ -0,0 +1,11 @@
+use unchecked_index::unchecked_index;
+
+#[test]
+fn unchecked_access() {
+    let mut xs = [0];
+    unsafe {
+        let mut xs = unchecked_index(&mut xs);
+        xs[0] += 1;
+        assert_eq!(xs[0], 1);
+    }
+}