feat: add Singlebox app

[quanglam2807]

App URL: https://singleboxapp.com
Screenshots:

• https://singleboxapp.com/images/demos/main.png
• https://singleboxapp.com/images/demos/single-window.png
• https://singleboxapp.com/images/demos/catalog.png
• https://singleboxapp.com/images/demos/custom-apps.png
• https://singleboxapp.com/images/demos/notifications.png
• https://singleboxapp.com/images/demos/email-client.png
• https://singleboxapp.com/images/demos/customization.png

[vhashimotoo]

Thanks for creating PR!

We found some errors what's need to be fixed for your app be added:

The app yaml file is not matching required code style

We strongly required all apps be styled with default Prettier style. You can fix that by running yarn prettier --write. After that commit your changes. (Please do not use the force-push, we anyway squash all changes on merge).
If you aren't able to fix style changes you can use the ready styled input for your app:

name: Singlebox
description: 'All Your Apps in One Single Window.'
website: 'https://singleboxapp.com/'
repository: 'https://github.com/quanglam2807/singlebox'
screenshots:
  - imageUrl: 'https://raw.githubusercontent.com/quanglam2807/singlebox/1fac7b931a4bb44046d882f4fea4df2a0cd94676/docs/images/demos/main.png'
    caption: 'Singlebox'
  - imageUrl: 'https://raw.githubusercontent.com/quanglam2807/singlebox/1fac7b931a4bb44046d882f4fea4df2a0cd94676/docs/images/demos/single-window.png'
    caption: 'Single Window - Switch between multiple apps quickly.'
  - imageUrl: 'https://raw.githubusercontent.com/quanglam2807/singlebox/1fac7b931a4bb44046d882f4fea4df2a0cd94676/docs/images/demos/catalog.png'
    caption: 'Catalog - Add apps quickly from our curated catalog.'
  - imageUrl: 'https://raw.githubusercontent.com/quanglam2807/singlebox/1fac7b931a4bb44046d882f4fea4df2a0cd94676/docs/images/demos/custom-apps.png'
    caption: 'Custom Apps - Create apps easily from any websites.'
  - imageUrl: 'https://raw.githubusercontent.com/quanglam2807/singlebox/1fac7b931a4bb44046d882f4fea4df2a0cd94676/docs/images/demos/notifications.png'
    caption: 'Notifications - Control notifications with scheduling.'
  - imageUrl: 'https://raw.githubusercontent.com/quanglam2807/singlebox/1fac7b931a4bb44046d882f4fea4df2a0cd94676/docs/images/demos/email-client.png'
    caption: 'Email Client - The same email apps you love, but better!'
  - imageUrl: 'https://raw.githubusercontent.com/quanglam2807/singlebox/1fac7b931a4bb44046d882f4fea4df2a0cd94676/docs/images/demos/customization.png'
    caption: 'Customization - Make yourself at home!'
keywords:
  - 'single window'
  - 'email client'
  - messaging
  - chat
  - browser
  - productivity
category: Productivity

After fixing that errors you can ping the person who requested these changes for
future next steps.

---

That message sent automatically, if you think that message contain error or
misinterpreted please ping @HashimotoYT.

[Toinane]

Hey @quanglam2807 can you fix your app yaml file if possible? I can't accept your app submission otherwise.

[Toinane]

Hey there, since I haven't received a response yet, I'm gonna have to close this PR.
Feel free to reopen it or make a new PR.
Thank you!