Feature: Cache results for up to 7 days

[Obscurely]

The idea is to use sled, a fast rust native db.

For each request make a new entry and assign it all the results got.

Whenever making a search Falion should check if there are any already cached results for this specific requests:

• if there are check how old they are
  • if they are older than 7 days get new results and replace the existing ones.
  • if they are NOT older than 7 days display the cached results
• if there AREN'T any get new results and cache them.

This should be very fast and not create any performance regression bigger than... let's say 100ms which from my past experience with sled should be very achievable, I would say under 50ms should be possible.