Add rss feed from bot

[technetos]

Add rss parsing support in the bot such that we can parse various feeds like the blog, inside rust, and TWiR and display them in a channel.

Relevant crates:
https://crates.io/crates/rss

Actionable steps:

• Add a new module called rss.rs or similar
• Add a command to add rss feed urls to the bot, ?rss add url... or similar
• Add a command to fetch the rss feeds and display them in the discord channel, ?rss update or similar
  • Continually adding the feeds as new messages in the discord channel can get cumbersome. Its probably best to only post the message once and edit it when we need to refresh the feeds.

Todo:

• Create the channel in the rust discord for the feeds, Announcements or similar

Additional details:

• Adding a new rss feed should be limited to WG & Teams
• Updating the rss feeds should be limited to WG & Teams