add about page. fixes #15

src/app/About.vue

@@ -0,0 +1,40 @@
+<template>
+  <b-modal size="lg" hide-header hide-footer :visible="visible" @change="$emit('close')">
+    <div style="width: 200px" class="mx-auto mb-3">
+      <Logo />
+    </div>
+    <div class="text-center">
+      <ExternalLink :href="url">
+        GitHub <Icon icon="box-arrow-up-right" />
+      </ExternalLink>
+      <p>
+        Licensed under the AGPLv3 license.
+      </p>
+      <div>Build: {{ build }}</div>
+      <div>Build date: {{ buildDate }}</div>
+    </div>
+    <div class="d-flex justify-content-end">
+      <button class="btn btn-secondary" @click="$emit('close')">
+        Close
+      </button>
+    </div>
+  </b-modal>
+</template>
+<script lang="ts">
+  import Vue from 'vue'
+  import Logo from './Logo.vue'
+
+  export default Vue.extend({
+    components: {
+      Logo,
+    },
+    props: {
+      visible: { type: Boolean, required: true },
+    },
+    computed: {
+      build: () => process.env.VUE_APP_BUILD,
+      buildDate: () => process.env.VUE_APP_BUILD_DATE,
+      url: () => 'https://github.com/tamland/airsonic-frontend'
+    },
+  })
+</script>

src/app/TopNav.vue

@@ -25,22 +25,34 @@
         <b-dropdown-item :href="`${server}/settings.view`">
           Server settings
         </b-dropdown-item>
+        <b-dropdown-item-button @click="showAboutModal = true">
+          About
+        </b-dropdown-item-button>
+        <b-dropdown-divider />
         <b-dropdown-item-button @click="logout">
           Log out
         </b-dropdown-item-button>
       </b-dropdown>
     </template>
+    <About :visible="showAboutModal" @close="showAboutModal = false" />
   </div>
 </template>
 <script lang="ts">
   import Vue from 'vue'
   import { mapActions, mapState } from 'vuex'
+  import About from './About.vue'
   import SearchForm from '@/search/SearchForm.vue'
 
   export default Vue.extend({
     components: {
+      About,
       SearchForm,
     },
+    data() {
+      return {
+        showAboutModal: false
+      }
+    },
     computed: {
       ...mapState([
         'server',