chore(docs): Update getting started contract tutorial (#4588)

This PR add missing instruction to add the storage struct.

docs/docs/developers/getting_started/aztecnr-getting-started.md

@@ -92,6 +92,12 @@ We are also using `balance_utils` from this import, a useful library that allows
 
 This allows us to store our counter in a way that acts as an integer, abstracting the note logic.
 
+## Declare storage
+
+Add this below the imports. It declares the storage variables for our contract. We are going to store a mapping of values for each `AztecAddress`.
+
+#include_code storage_struct /noir-projects/noir-contracts/contracts/counter_contract/src/main.nr rust
+
 ## Keep the counter private
 
 Now we’ve got a mechanism for storing our private state, we can start using it to ensure the privacy of balances.

noir-projects/noir-contracts/contracts/counter_contract/src/main.nr

@@ -20,11 +20,9 @@ contract Counter {
     // docs:end:imports
 
     // docs:start:storage_struct
-
     struct Storage {
         counters: Map<AztecAddress, EasyPrivateUint>,
     }
-
     // docs:end:storage_struct
 
     // docs:start:constructor