enhancement: store block timestamps

[joel-u410]

It'll be good to store timestamp for blocks along with height so that transactions and balances can be queried with timestamps.

I propose introducing a blocks table to capture that data. (Will submit a PR for this soon)

At this point, since mainnet has now launched, I assume we should introduce new migrations rather than modifying existing ones, correct? (cc @mateuszjasiuk @Fraccaman)

[Fraccaman]

Yeah, this is something @mateuszjasiuk is working on! Yeah now we need to introduce new migrations :)

[joel-u410]

Yeah, this is something @mateuszjasiuk is working on! Yeah now we need to introduce new migrations :)

Ah .. I just wrote it myself and opened a PR here: #190 :)

[mateuszjasiuk]

That's fine! I should've added issue. Anyways, I think as a rule of thumb maybe we should add a label like: "ready" or sth, to indicate that issue makes sense and we do not double the work.