Add apply and reset themes to top of theme tab

src/components/settings_modal/tabs/theme_tab/theme_tab.vue

@@ -1,6 +1,21 @@
 <template>
   <div class="theme-tab">
     <div class="presets-container">
+      <div class="apply-container">
+        <button
+          class="btn button-default submit"
+          :disabled="!themeValid"
+          @click="setCustomTheme"
+        >
+          {{ $t('general.apply') }}
+        </button>
+        <button
+          class="btn button-default"
+          @click="clearAll"
+        >
+          {{ $t('settings.style.switcher.reset') }}
+        </button>
+      </div><br>
       <div class="save-load">
         <div
           v-if="themeWarning"