export type, store slot as string

[21e8]

hi!

I was told about this and think its a great project, might also use this myself.
browsing the code I found two pretty simple things:

• we never export the db connection type and use any, whereas we really have it
• we convert slot to bigint. the table col is numeric, pretty sure it expects a string. .toString() should work for both, numbers and bigints, so we could even upgrade to web3.js 2.0 bigints (if they are even being returned here)

Right now I just wanted to fix the type errors. If you prefer strings over bigints or the other way round, let me know and I can set it straight everywhere.

regards
0xAlice

EDIT: I did some more typescript stuff. we're handling bigint differently, I think to be consistent we either have to use strings everywhere or change the schema have the option {mode: "bigint"} everywhere.