add link to lab sign-up sheet

docs/pages/schedule_static.html

@@ -203,7 +203,7 @@ <h1>Schedule</h1>
     </td>
     <td style="background-color: rgba(101, 123, 131, 0.1);">
         <strong><em>Sign-up:</em></strong>
-        <p style="margin-top:0;margin-bottom:0;font-size:100%"> Select one of the offered lab session days according to your schedule</p>
+        <p style="margin-top:0;margin-bottom:0;font-size:100%"> Select one of the offered lab session days and times according to your schedule from <a href="https://docs.google.com/spreadsheets/d/1w9WryKCfZ--RGjEujGyqUGi36t-x5X79A_v0mTyAI64/edit?usp=sharing">this sheet</a>.</p>
     </td>
     <td style="background-color: rgba(154, 205, 50, 0.1);">
         <strong><em>Note:</em></strong>
@@ -774,4 +774,4 @@ <h1>Schedule</h1>
       crossorigin="anonymous"
     ></script>
   </body>
-</html>
+</html>