Add fetchJobs option to parallelize submodule updates

src/git-source-settings.ts

@@ -34,6 +34,11 @@ export interface IGitSourceSettings {
    */
   fetchDepth: number
 
+  /**
+   * The number of fetches to perform simultaneously when updating submodules
+   */
+  fetchJobs: number
+
   /**
    * Indicates whether to fetch LFS objects
    */