Add excursion option

Change-Id: I70133582d92c3a6385fefb46a99743d47f68cd46
diff --git a/templates/register.htm b/templates/register.htm
index ca8eeca..61cebea 100644
--- a/templates/register.htm
+++ b/templates/register.htm
@@ -604,6 +604,15 @@
     </div>
     <div id="lunchHelp2" class="form-text fs-4">Please note that lunch must be ordered and paid for in advance and unfortunately cannot be purchased spontaneously on site.</div>
 
+    <div class="form-outline mb-3">
+        <label class="form-label fw-bold" for="excursion">Excursion</label>
+        <div class="form-group form-check">
+            <input type="checkbox" class="form-check-input" name="excursion" id="excursion" <?php echo isset($_POST[ 'excursion']) ? 'checked' : '' ?> oninput="update_total_due()" value="excursion">
+            <label class="form-check-label fs-4" for="excursion">I would like to participate in the excursion on the afternoon of Friday, 21 July for the price of <strong>€&#160;<span id="excursion_price"><?php echo $EXCURSION; ?></span></strong>.
+            </label>
+        </div>
+    </div>
+
     <div class="form-outline col-md-12">
         <label class="form-label fw-bold" for="exampleInputAmount">Total Amount in Euro to be paid</label>
         <div class="input-group">