docs(audit_config): How to use it (#2739)

docs/developer-guide/checks.md

@@ -20,7 +20,7 @@ Inside that folder, we need to create three files:
 The Prowler's check structure is very simple and following it there is nothing more to do to include a check in a provider's service because the load is done dynamically based on the paths.
 
 The following is the code for the `ec2_ami_public` check:
-```python
+```python title="Check Class"
 # At the top of the file we need to import the following:
 # - Check class which is in charge of the following:
 #   - Retrieve the check metadata and expose the `metadata()`
@@ -160,6 +160,38 @@ class Check(ABC, Check_Metadata_Model):
         """Execute the check's logic"""
 ```
 
+### Using the audit config
+
+Prowler has a [configuration file](../tutorials/configuration_file.md) which is used to pass certain configuration values to the checks, like the following:
+
+```python title="ec2_securitygroup_with_many_ingress_egress_rules.py"
+class ec2_securitygroup_with_many_ingress_egress_rules(Check):
+    def execute(self):
+        findings = []
+
+        # max_security_group_rules, default: 50
+        max_security_group_rules = ec2_client.audit_config.get(
+            "max_security_group_rules", 50
+        )
+        for security_group in ec2_client.security_groups:
+```
+
+```yaml title="config.yaml"
+# AWS Configuration
+aws:
+  # AWS EC2 Configuration
+
+  # aws.ec2_securitygroup_with_many_ingress_egress_rules
+  # The default value is 50 rules
+  max_security_group_rules: 50
+```
+
+As you can see in the above code, within the service client, in this case the `ec2_client`, there is an object called `audit_config` which is a Python dictionary containing the values read from the configuration file.
+
+In order to use it, you have to check first if the value is present in the configuration file. If the value is not present, you can create it in the `config.yaml` file and then, read it from the check.
+> It is mandatory to always use the `dictionary.get(value, default)` syntax to set a default value in the case the configuration value is not present.
+
+
 ## Check Metadata
 
 Each Prowler check has metadata associated which is stored at the same level of the check's folder in a file called A `check_name.metadata.json` containing the check's metadata.