Add test for indexing
diff --git a/tests/indexing.rs b/tests/indexing.rs
new file mode 100644
index 0000000..ebbed77
--- /dev/null
+++ b/tests/indexing.rs
@@ -0,0 +1,8 @@
+use text_size::*;
+
+#[test]
+fn main() {
+    let range = TextRange::default();
+    &""[range];
+    &String::new()[range];
+}