Add configuration

Currently, some elements of configuration should be done manually by the user or hardcoded in `arion-compose.nix`:
- NFT_STORAGE_KEY_HERE
- marketplace wallet address in ODC filter (`"--block-filter" "{\"address\": \"addr_test1wr05mmuhd3nvyjan9u4a7c76gj756am40qg7vuz90vnkjzczfulda\"}"`)

