feat: add folder upload (#981)

* feat: folder upload
fix filebrowser/filebrowser#741

* fix: apply gofmt formater

* feat: upload button prompt

* feat: empty folder upload

frontend/src/components/prompts/Upload.vue

@@ -0,0 +1,37 @@
+<template>
+  <div class="card floating">
+    <div class="card-title">
+      <h2>{{ $t('prompts.upload') }}</h2>
+    </div>
+
+    <div class="card-content">
+      <p>{{ $t('prompts.uploadMessage') }}</p>
+    </div>
+
+    <div class="card-action full">
+      <div @click="uploadFile" class="action">
+        <i class="material-icons">insert_drive_file</i>
+        <div class="title">File</div>
+      </div>
+      <div @click="uploadFolder" class="action">
+        <i class="material-icons">folder</i>
+        <div class="title">Folder</div>
+      </div>
+    </div>
+  </div>
+</template>
+
+<script>
+
+export default {
+  name: 'upload',
+  methods: {
+    uploadFile: function () {
+      document.getElementById('upload-input').click()
+    },
+    uploadFolder: function () {
+      document.getElementById('upload-folder-input').click()
+    }
+  }
+}
+</script>