adds ProgressIndicator component

components/ProgressIndicator.vue

+<template>
+  <div>
+    <v-overlay
+      :value="isInProgress"
+      :opacity="dark ? 0.5 : 0.05"
+    >
+      <v-progress-circular
+        indeterminate
+        class="center-absolute"
+      />
+    </v-overlay>
+  </div>
+</template>
+
+<style>
+  .center-absolute {
+    position: fixed;
+    top: 50%;
+    left: 50%;
+    margin-top: -16px;
+    margin-left: -16px;
+  }
+</style>
+
+<script lang="ts">
+import { Component, Vue, Prop } from 'nuxt-property-decorator'
+
+@Component
+export default class ProgressIndicator extends Vue {
+  @Prop({
+    default: false,
+    required: false,
+    type: Boolean
+  })
+  // @ts-ignore
+  readonly value!: boolean
+
+  @Prop({
+    default: false,
+    required: false,
+    type: Boolean
+  })
+  // @ts-ignore
+  readonly dark!: boolean
+
+  get isInProgress (): boolean {
+    return this.value
+  }
+}
+</script>