Add getBlockConfidence rpc endpoint (#6350)

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book/src/api-reference/jsonrpc-api.md

@@ -17,6 +17,7 @@ To interact with a Solana node inside a JavaScript application, use the [solana-
 * [confirmTransaction](jsonrpc-api.md#confirmtransaction)
 * [getAccountInfo](jsonrpc-api.md#getaccountinfo)
 * [getBalance](jsonrpc-api.md#getbalance)
+* [getBlockConfidence](jsonrpc-api.md#getblockconfidence)
 * [getClusterNodes](jsonrpc-api.md#getclusternodes)
 * [getEpochInfo](jsonrpc-api.md#getepochinfo)
 * [getGenesisBlockhash](jsonrpc-api.md#getgenesisblockhash)
@@ -149,6 +150,34 @@ curl -X POST -H "Content-Type: application/json" -d '{"jsonrpc":"2.0", "id":1, "
 {"jsonrpc":"2.0","result":0,"id":1}
 ```
 
+### getBlockConfidence
+
+Returns confidence for particular block
+
+#### Parameters:
+
+* `u64` - block, identified by Slot
+
+#### Results:
+
+The result field will be an array with two fields:
+
+* Confidence
+  * `null` - Unknown block
+  * `object` - BankConfidence
+    * `array` - confidence, array of u64 integers logging the amount of cluster stake in lamports that has voted on the block at each depth from 0 to `MAX_LOCKOUT_HISTORY`
+* 'integer' - total active stake, in lamports, of the current epoch
+
+#### Example:
+
+```bash
+// Request
+curl -X POST -H "Content-Type: application/json" -d '{"jsonrpc":"2.0","id":1, "method":"getBlockConfidence","params":[5]}' http://localhost:8899
+
+// Result
+{"jsonrpc":"2.0","result":[{"confidence":[0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,10,32]},42],"id":1}
+```
+
 ### getClusterNodes
 
 Returns information about all the nodes participating in the cluster
@@ -808,4 +837,3 @@ Unsubscribe from signature confirmation notification
 // Result
 {"jsonrpc": "2.0","result": true,"id": 1}
 ```
-