Add Caching

[ckoopmann]

Not sure if we even need this in the first place but I noticed that in eth-analysis-rs there is a caching logic, presumably to reduce the number of db requests and thereby enhance the performance.

@alextes Would love to hear if you have any thoughts on this. Priority / Necessity of caching as well as wether we can just more or less copy the caching approach of eth-analysis-rs or do it differently.

[alextes]

I don't think I'd copy the same. The eth-analysis-rs caching is quite sophisticated because it very specifically wants:

• one cache writer which updates whenever new data is available, and so every 12s
• many cache readers which get tipped off and update in unison as data becomes available

Depending on the desired feature by users, "request from the DB every time" plus a caching header cloudflare respects may be enough already.