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

Sources/ResgenSwift/Generate/Extensions/StringExtensions.swift

@@ -0,0 +1,18 @@
+//
+//  StringExtensions.swift
+//  
+//
+//  Created by Thibaut Schmitt on 31/08/2022.
+//
+
+import Foundation
+
+extension String {
+    
+    func prependIfRelativePath(_ prependPath: String) -> String {
+        if self.hasPrefix("/") {
+            return self
+        }
+        return prependPath + self
+    }
+}