feature request: cache nzb grabs on self-hosted instances

[webstreamr]

Checklist

• I checked that this feature has not been requested before
• I checked that this feature is not in the "Not planned" list
• This feature will benefit the majority of users

Problem Description / Use Case

caching nzb grabs could be very useful for free indexers with low limits where instead of 2-4 grabs you end up only with a single one when opening a link

I realize though that this could be tricky for the proxied grabs to do, especially if the context of a nzb grab is missing

Proposed Solution

add a simple url - nzb cache which can be configured via .env. TTL can and maybe should be super low even, it would just help massively with how stremio URL requesting architecture works to avoid multi grabs.

additionally, it could be also locked down by user id if needed, but maybe that's overkill