Related: #5

Additional configuration option to automatically use instances from /api/instances.

Prioritize the user-configured list, deduplicate the /api/instances one (to avoid trying one instance twice, listed in both user-configured and discovery list).

Sort by 'is listed in docs', then by a value of non-blocked 'uptime' (optionally the value is increased by added length of operation (preferring 99% 2y instance to 100% 2d)).

If favour-old-instance is not adopted, ban all instances newer than 30d (the ones not in docs listing). This is to avoid a new instance getting a friendly ddos on first launch, giving the hoster the impression that Bibliogram is useless.

This would also need a configuration option of advertising assistant availability for both cached and new requests.