Generate JSON files to be consumed by Vue.js UI

[dan-niles]

Since we are now switching to the Vue.js approach for the UI of the ZIM, we need to generate JSON files which contain data about the youtube channel/playlist and the videos in it. These JSON files will then be consumed by the Vue.js UI, and the relevant content will be rendered.

The following types of JSON files need to be generated by the scraper:

• Channel Metadata
• List of all videos in the channel (Uploads of channel)
• List of playlists in the channel
• The videos inside specific playlists
• Metadata for each video