Add test for strings with numbers

Proposed by @thatblindgeye.

09_palindromes/palindromes.spec.js

@@ -19,4 +19,7 @@ describe('palindromes', () => {
   test.skip('doesn\'t just always return true', () => {
     expect(palindromes('ZZZZ car, a man, a maracaz.')).toBe(false);
   });
+  test('works with numbers in a string', () => {
+    expect(palindromes('rac3e3car')).toBe(true);
+  });
 });