fix: update override field for all queries doc

Author: SockworkOrange

docs/03_Usage.md

@@ -11,6 +11,7 @@
 | Override            | values: A nested override value like [this](#override-option). | Yes | Allows you to override the generated C# data types for specific columns in specific queries. This option accepts a `query_name:column_name` mapping and the overriden data type. |                                                                                     |
 
 ### Override option
+Override for a specific query:
 ```yaml
 overrides:
   - column: "<query-name>:<field-name>"
@@ -19,6 +20,15 @@ overrides:
       notNull: true|false
 ```
 
+Override for all queries:
+```yaml
+overrides:
+  - column: "*:<field-name>"
+    csharp_type:
+      type: "<csharp-datatype>"
+      notNull: true|false
+```
+
 ## Supported Features
 - ✅ means the feature is fully supported.
 - 🚫 means the database does not support the feature.