Merge #17102: doc: Add missing indexes/blockfilter/basic to doc/files.md

fa191c0 doc: Add missing indexes/blockfilter/basic/ to doc/files.md (MarcoFalke)

Pull request description:

ACKs for top commit:
  hebasto:
    ACK fa191c0
  fanquake:
    ACK fa191c0

Tree-SHA512: ea30776224e4a26bc6f60c9c65361f0b9d7b2b4f844c6d2aefd108f852dd7d813963df631a8ed20daea5acae7a23d0b405d12a162f90a6f61a3db236f5beed45

Author: fanquake

doc/files.md

@@ -46,6 +46,8 @@ Subdirectory       | File(s)               | Description
 `blocks/`          | `revNNNNN.dat`<sup>[\[2\]](#note2)</sup> | Block undo data (custom format)
 `chainstate/`      | LevelDB database      | Blockchain state (a compact representation of all currently unspent transaction outputs and some metadata about the transactions they are from)
 `indexes/txindex/` | LevelDB database      | Transaction index; *optional*, used if `-txindex=1`
+`indexes/blockfilter/basic/db/` | LevelDB database      | Blockfilter index LevelDB database for the basic filtertype; *optional*, used if `-blockfilterindex=basic`
+`indexes/blockfilter/basic/`    | `fltrNNNNN.dat`<sup>[\[2\]](#note2)</sup> | Blockfilter index filters for the basic filtertype; *optional*, used if `-blockfilterindex=basic`
 `wallets/`         |                       | [Contains wallets](#multi-wallet-environment); can be specified by `-walletdir` option; if `wallets/` subdirectory does not exist, a wallet resides in the data directory
 `./`               | `banlist.dat`         | Stores the IPs/subnets of banned nodes
 `./`               | `bitcoin.conf`        | Contains [configuration settings](bitcoin-conf.md) for `bitcoind` or `bitcoin-qt`; can be specified by `-conf` option