fix: add label to textarea

To increase accessibility.

Signed-off-by: Conrad Zelck <git@simpel.cc>

index.html

@@ -42,7 +42,8 @@
         <label for="unique">output unique lines only</label>
       </div>
     </div>
-    <textarea autofocus placeholder="fill in lines to sort here …" spellcheck="false" autocomplete="off"></textarea>
+    <label for="textarea">Lines to sort or already sorted:</label>
+    <textarea id="textarea" autofocus placeholder="fill in lines to sort here …" spellcheck="false" autocomplete="off"></textarea>
   </main>
 </body>
 <script src="script.js"></script>