WebHost: Fix "Add" button for Progression Balancing causing a weird redirect

This "add" button is part of a form, which causes it to submit the form, because the default type for a button is "submit".

This PR changes the type of the button to "button", which causes it to not submit the form and just execute its normal effect.

(An alternative would be `event.preventDefault()` but that seems less clean to me, but also I'm not a HTML/JS dev)

WebHostLib/templates/weightedOptions/macros.html

@@ -47,7 +47,7 @@
         {% endif %}
         <div class="add-option-div">
             <input type="number" class="range-option-value" data-option="{{ option_name }}" />
-            <button class="add-range-option-button" data-option="{{ option_name }}">Add</button>
+            <button type="button" class="add-range-option-button" data-option="{{ option_name }}">Add</button>
         </div>
     </div>
     <table class="range-rows" data-option="{{ option_name }}">