Update env-vars.mdx

Added note about enabling transaction indexing

packages/docs/pages/operators/ledger/env-vars.mdx

@@ -3,7 +3,7 @@ import Expandable from "../../../components/Expandable";
 
 # Node Configuration
 
-By default, whenever the namada ledger is started, it will apply the confirguration found in the ledger configuration file `$BASE_DIR/$CHAIN_ID/config.toml`.
+By default, whenever the namada ledger is started, it will apply the configuration found in the ledger configuration file `$BASE_DIR/$CHAIN_ID/config.toml`.
 
 An example of a ledger configuration file is displayed below.
 
@@ -163,4 +163,13 @@ In principle, even `.` can be used for environment variable names.
 However, in Bash, only the double underscore form can be 
 used, because Bash doesn't allow dots in environment variable names. 
 Therefore, we omit the dot form.
-</Callout>
+</Callout>
+
+### Optional Functions
+
+**Enable Transaction Indexing**: If you would like your validator to index transactions, set the `indexer` under `[ledger.cometbft.tx_index]` from `null` to `kv`. 
+
+```shell copy
+[ledger.cometbft.tx_index]
+indexer = "kv"
+```