List page for weekly emails

[mdirolf]

Would be good to have some other method to view old weekly emails other than just paginating through one by one. Perhaps a page per year

[zphixon]

Hello! I've started some work on this and I'm wondering if there's some potential improvements around how weekly emails are handled (as opposed to regular articles).

Right now, I'm retrieving weekly emails by querying for articles whose slugs start with weekly-email-${year}, then parsing out the publication date from the slug to display on the year's list.

I think it would make more sense to differentiate weekly emails in firestore, as well as include the publication date.

[mdirolf]

@zphixon I think you're probably right that it would've made sense to make a new collection for these. But since your PR seems to accomplish what we need I think we can punt for now on doing any sort of migration.