fix: define type of buttons

Both buttons are no type submit but that is defined aas default. So I
wrote type="button" now to be right according html5.

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

index.html

@@ -34,9 +34,9 @@
       <p>If you set the option "output unique lines only" all lines existing more then once are deleted.</p>
     </details>
     <div class="flex">
-      <button class="button pastesortunique" title="click: paste + sort + unique + copy to clipboard" onclick="paste()">Paste, Sort &amp; Copy [1]</button>
+      <button type="button" class="button pastesortunique" title="click: paste + sort + unique + copy to clipboard" onclick="paste()">Paste, Sort &amp; Copy [1]</button>
       <span class="between_buttons">or</span>
-      <button class="button sortunique" title="click: sort + unique + copy to clipboard" onclick="sort_and_copy()">Sort &amp; Copy [2]</button>
+      <button type="button" class="button sortunique" title="click: sort + unique + copy to clipboard" onclick="sort_and_copy()">Sort &amp; Copy [2]</button>
       <div class="flexlabel">
         <input id="unique" type="checkbox" name="unique" checked>
         <label for="unique">output unique lines only</label>