Add Apple App Store badge to the README.md

[kinueng]

Hello,

I am a happy long time user of the iOS NewsBlur application. I wanted to add the Apple App Store badge to the README.md so that others know you can use NewsBlur on Apple mobile devices too.

Below is from the commit message

• Add a clickable badge for the NewsBlur Apple App Store page

• Use Apple's marketing website tool to get the App Store badge

  • https://tools.applemediaservices.com/app/463981119

• Used HTML elements   to add left padding to the Apple badge so that it aligns with the F-Droid badge. GitHub restricts what kind of inline styling is allowed in the README.md for security reasons. Inline styling of padding left is one of those attributes that get removed.

  • https://github.com/github/markup#github-markup

[kinueng]

Here is a quick link to preview how the Apple App Store badge renders on GitHub https://github.com/kinueng/NewsBlur#readme

[samuelclay]

Thanks for doing this!