because WSL2 Docker set 755 file permissions instead of 644, this results to the error.
Updated `Extension` class: replaced `pull()` with `fetch_and_reset_hard()` method.
Updated `apply_and_restart()` function: replaced `ext.pull()` with `ext.fetch_and_reset_hard()` function.
By creating a file called "preload.py" in an extension folder and declaring a preload(parser) method, we can add extra command-line args for an extension.
