Adding prettier ignore

Author: jagdish-15

exercises/practice/reverse-string/.docs/instructions.append.md

@@ -1,4 +1,6 @@
+<!-- prettier-ignore-start -->
 ~~~exercism/advanced
 If you solve this using the CLI, there are test cases that require you to deal with complex characters.
 You can optionally enable these tests by removing `.skip` from the test.
 ~~~
+<!-- prettier-ignore-end -->