OP ENV variable values defining

This instruction helps to find some values for OP ENV variables. Please, see the variables description first.

INDEXER_OPTIMISM_L1_SYSTEM_CONFIG_CONTRACT: this is the address of SystemConfig smart contract that contains most of the configuration parameters used by OP fetcher modules. Its address is usually found in chain's online docs. If there are no docs available, we need to ask chain's team for the SystemConfig contract address.
INDEXER_OPTIMISM_L1_BATCH_BLOCKSCOUT_BLOBS_API_URL: note that if the OP chain uses EIP-4844 blobs as data storage, this env is required. Also, the following envs must also be defined in this case: INDEXER_BEACON_RPC_URL, INDEXER_BEACON_BLOB_FETCHER_REFERENCE_SLOT, INDEXER_BEACON_BLOB_FETCHER_REFERENCE_TIMESTAMP, INDEXER_BEACON_BLOB_FETCHER_SLOT_DURATION - they are used by the batch indexing module as a fallback source of blob data and for retrieving the blob data in realtime from L1. Their values can be clarified by Blockscout team. Currently, the following ones are actual for some L1 chains:

Ethereum Mainnet:
```
INDEXER_BEACON_BLOB_FETCHER_REFERENCE_SLOT=8500000
INDEXER_BEACON_BLOB_FETCHER_REFERENCE_TIMESTAMP=1708824023
INDEXER_BEACON_BLOB_FETCHER_SLOT_DURATION=12
```
Sepolia:
```
INDEXER_BEACON_BLOB_FETCHER_REFERENCE_SLOT: 4400000
INDEXER_BEACON_BLOB_FETCHER_REFERENCE_TIMESTAMP: 1708533600
INDEXER_BEACON_BLOB_FETCHER_SLOT_DURATION: 12
```
Holesky:
```
INDEXER_BEACON_BLOB_FETCHER_REFERENCE_SLOT=1000000
INDEXER_BEACON_BLOB_FETCHER_REFERENCE_TIMESTAMP=1707902400
INDEXER_BEACON_BLOB_FETCHER_SLOT_DURATION=12
```
INDEXER_OPTIMISM_L2_BATCH_GENESIS_BLOCK_NUMBER: usually it's found in the superchain registry in superchains.chains[i].genesis.l2.number, e.g. for OP Mainnet it's 105235063, but for most of the new OP chains it's equal to 0 as they start with BedRock upgrade activated from scratch.
INDEXER_OPTIMISM_L1_OUTPUT_ORACLE_CONTRACT: the address of this contract can be found in chain's online docs. If there are no docs available, we need to ask chain's team for that. This address is not actual (and can be ommitted) for OP chains that started with FaultProofs upgrade activated from genesis block.

The rest OP ENV variable values are obvious. Those ones having default values can be ommitted for most cases.