[Local folder] Allow all image types

Implementing review feedback from PR #145

#145 (comment)

src/adapter/localFolder.ts

@@ -98,7 +98,7 @@ class LocalFolderAdapter extends BaseAdapter {
             }
 
             const contentType = info.get_content_type();
-            if (contentType === 'image/png' || contentType === 'image/jpeg')
+            if (contentType && contentType.startsWith('image/'))
                 files.push(child);
         }