docs: add docs for the feature added in #998 (#1040)

Author: alessiodionisi

docs/reference/config.md

@@ -17,6 +17,9 @@ packages:
     emit_empty_slices: false
     emit_json_tags: true
     json_tags_case_style: "camel"
+    output_db_file_name: "db.go"
+    output_models_file_name: "models.go"
+    output_querier_file_name: "querier.go"
 ```
 
 Each package document has the following keys:
@@ -44,6 +47,14 @@ Each package document has the following keys:
   - If true, add JSON tags to generated structs. Defaults to `false`.
 - `json_tags_case_style`:
   - `camel` for camelCase, `pascal` for PascalCase, `snake` for snake_case or `none` to use the column name in the DB. Defaults to `none`.
+- `output_db_file_name`:
+  - Customize the name of the db file. Defaults to `db.go`.
+- `output_models_file_name`:
+  - Customize the name of the models file. Defaults to `models.go`.
+- `output_querier_file_name`:
+  - Customize the name of the querier file. Defaults to `querier.go`.
+- `output_files_suffix`:
+  - If specified the suffix will be added to the name of the generated files.
 
 ## Type Overrides