feature request: memory metrics

[appliedprivacy]

It would be nice to have birds memory metrics included in bird_exporter

bird> show memory
BIRD memory usage
                  Effective    Overhead
Routing tables:    188.1 MB   2957.9 kB
Route attributes:  106.3 MB     16.0 MB
Protocols:        1462.8 kB     32.3 kB
Standby memory:      0.0  B   2024.0 kB
Total:             295.9 MB     20.9 MB

[ewpratten]

:+1: on this from me too. Memory reporting would be nice