add confirm prompt for template upload via URL

app/javascript/application.js

@@ -54,6 +54,7 @@ import GoogleDriveFilePicker from './elements/google_drive_file_picker'
 import OpenModal from './elements/open_modal'
 import BarChart from './elements/bar_chart'
 import FieldCondition from './elements/field_condition'
+import ConfirmUpload from './elements/confirm_upload'
 
 import * as TurboInstantClick from './lib/turbo_instant_click'
 
@@ -146,6 +147,7 @@ safeRegisterElement('google-drive-file-picker', GoogleDriveFilePicker)
 safeRegisterElement('open-modal', OpenModal)
 safeRegisterElement('bar-chart', BarChart)
 safeRegisterElement('field-condition', FieldCondition)
+safeRegisterElement('confirm-upload', ConfirmUpload)
 
 safeRegisterElement('template-builder', class extends HTMLElement {
   connectedCallback () {

app/javascript/elements/confirm_upload.js

@@ -0,0 +1,27 @@
+import { target, targetable } from '@github/catalyst/lib/targetable'
+
+export default targetable(class extends HTMLElement {
+  static [target.static] = [
+    'prompt',
+    'processing',
+    'logo'
+  ]
+
+  connectedCallback () {
+    this.form.addEventListener('submit', this.onSubmit)
+  }
+
+  disconnectedCallback () {
+    this.form.removeEventListener('submit', this.onSubmit)
+  }
+
+  onSubmit = () => {
+    this.prompt.classList.add('hidden')
+    this.processing.classList.remove('hidden')
+    this.logo.classList.add('animate-bounce')
+  }
+
+  get form () {
+    return this.querySelector('form')
+  }
+})