Add docs for Attestant apis

Author: mariavarvaroi

book/SUMMARY.md

@@ -13,7 +13,8 @@
 - [Ethereum](build-your-staking-dapp/ethereum/README.md)
   - [Overview](build-your-staking-dapp/ethereum/overview.md)
   - [Pooled Staking Methods](build-your-staking-dapp/ethereum/pooled_staking_methods.md)
-  - [Native Staking Methods](build-your-staking-dapp/ethereum/native_staking_methods.md)
+  - [Native Staking Methods (SDK)](build-your-staking-dapp/ethereum/native_staking_methods.md)
+  - [Native Staking Methods (API)](build-your-staking-dapp/ethereum/native_staking_attestant_endpoints.md)
   - [Pooled Staking](build-your-staking-dapp/ethereum/pooled_staking_overview.md)
   - [Native Staking](build-your-staking-dapp/ethereum/native_staking_overview.md)
   - [Delegation Tracking](build-your-staking-dapp/ethereum/delegation-tracking.md)