Deno's cache API does not respect expiry dates.
This meant that feeds were cached much longer than intended.
This PR implments a manual cache handling instead of relying on
Deno's implementation. Relevant issue: https://github.com/denoland/deno/issues/25795
Not the most elegant solution. But it works at the expense of old episodes.
I should think of something better at some point. Left some ideas in the code
for future reference.
Olav Sundfør
Tim Hårek Andreassen