ui-cosmetics: use monospace font for the textboxes in tab-settings

src/common/ui/setting-text.vue

@@ -1,5 +1,5 @@
 <template>
-  <textarea v-model="value" @change="onChange" :disabled="disabled" />
+  <textarea class="monospace-font" v-model="value" @change="onChange" :disabled="disabled" />
 </template>
 
 <script>

src/common/ui/style/style.css

@@ -242,6 +242,10 @@ button,
 
 .editor-code .CodeMirror {
   height: 100%;
+}
+
+.monospace-font,
+.editor-code .CodeMirror {
   /* Use `Courier New` to ensure ` ` has the same width as an original space. */
   font-family: "Fira Code", Menlo, Monaco, Consolas, "Liberation Mono", "Courier New", Courier, monospace;
 }