Allow relative paths in configuration file

Sources/Generator/Extensions/URL+Extensions.swift

@@ -50,4 +50,23 @@ extension URL {
         let attributes = try? FileManager.default.attributesOfItem(atPath: path)
         return (attributes?[.size] as? NSNumber)?.intValue
     }
+
+    func resolvingFolderTraversal() -> URL? {
+        var components = [String]()
+        absoluteString.components(separatedBy: "/").forEach { part in
+            if part == ".." {
+                if !components.isEmpty {
+                    _ = components.dropLast()
+                } else {
+                    components.append("..")
+                }
+                return
+            }
+            if part == "." {
+                return
+            }
+            components.append(part)
+        }
+        return URL(string: components.joined(separator: "/"))
+    }
 }