center scroll up button without using margins

Author: supalarry

frontend/src/components/shared/ScrollUpButton.vue

@@ -1,6 +1,6 @@
 <template>
   <!-- eslint-disable max-len -->
-  <div class="fixed bottom-0 w-full flex justify-center -ml-4 sm:-ml-16 lg:-ml-32">
+  <div class="fixed bottom-0 w-full flex justify-center left-0">
     <button v-if="showScroll"
             class="z-10 text-2xl text-white-matcha font-bold mb-10 w-12 h-12 rounded-full bg-purple-matcha"
             v-on:click="scrollUp()">