add latest_block_header to State

Co-authored-by: g11tech <develop@g11tech.io>

Author: unnawut

docs/client/containers.md

@@ -22,6 +22,7 @@ class Checkpoint(Container):
 class State(Container):
     config: Config
     slot: uint64
+    latest_block_header: BlockHeader
 
     latest_justified: Checkpoint
     latest_finalized: Checkpoint