Add dir loading for coherent feature

src/main/java/at/pcgamingfreaks/mkvaudiosubtitlechanger/impl/FileCollector.java

@@ -10,4 +10,13 @@ public interface FileCollector {
      * @return list of all files within the directory
      */
     List<File> loadFiles(String path);
+
+    /**
+     * Load all directories from path, but only until depth is reached.
+     *
+     * @param path leads to a directory which will be loaded recursively until depth
+     * @param depth limit directory crawling
+     * @return list of directory until depth
+     */
+    List<File> loadDirectories(String path, int depth);
 }