Add telephone number validation

production/form_validation.html

@@ -424,6 +424,13 @@
                         <input id="password2" type="password" name="password2" data-validate-linked="password" class="form-control col-md-7 col-xs-12" required="required">
                       </div>
                     </div>
+                    <div class="item form-group">
+                      <label class="control-label col-md-3 col-sm-3 col-xs-12" for="telephone">Telephone <span class="required">*</span>
+                      </label>
+                      <div class="col-md-6 col-sm-6 col-xs-12">
+                        <input type="tel" id="telephone" name="phone" required="required" data-validate-length-range="8,20" class="form-control col-md-7 col-xs-12">
+                      </div>
+                    </div>
                     <div class="item form-group">
                       <label class="control-label col-md-3 col-sm-3 col-xs-12" for="textarea">Textarea <span class="required">*</span>
                       </label>