spotify-dl-webui for user convenience

[krishsharma0413]

Hello @SathyaBhat,
I created spotify-dl-webui for spotify-dl for use convenience. I want you to test the Web UI yourself, give feedback if possible.

I also want you to add the repository link under spotify-dl README.md for the project to be used by the users who are just looking for an easy way to download Spotify playlists without going through the entire process.
I will be hosting the repository on a web server too later onward.

Thanks,
krish sharma