Add --project-directory option to generate command to easily use relative path

README.md

@@ -246,4 +246,18 @@ tags: []
 ...
 ```
 
+### Usage
 
+If you **don't** install ResgenSwift:
+
+```sh
+swift run -c release ResgenSwift generate path/to/configuration.yml --project-directory ${PROJECT_DIR}
+```
+
+If you install ResgenSwift:
+
+```sh
+resgen-swift generate path/to/configuration.yml --project-directory ${PROJECT_DIR}
+```
+
+> ⚠️ Every path in `configuration.yml` will be prepended by content of `--project-directory` if they are relative path (not starting with `/`)