feature: RSS -> permacast, bulk archive the back catalog

[xylophonez]

To make it easy for users to migrate their shows to permacast, we should enable an RSS feed import feature.

Ideally, when a user goes to 'add new show' from the navbar, one tab in that modal is 'import from RSS'.

• Parse the RSS channel metadata for the fields usually required in the form
• Loop through rss.channel.items, storing metadata for each and downloading the linked files for episodes
• Bulk upload them (cache in localStorage first?), and send SWC interactions the same way we do for individual episode uploads

[xylophonez]

being worked on here:

https://github.com/xylophonez/permacast-cli

needs updating when V3 comes out #46