Update README.md

Update README.md

Update README.md

Update README.md

add & update files.

Delete webhook.php

Delete update-tracking-item.php

Delete track.class.php

Delete list-all-trackings.php

Delete list-all-carriers.php

Delete get-tracking-results-of-a-single-tracking.php

Delete detect-a-carrier-by-tracking-code.php

Delete delete-a-tracking-item.php

Delete create-multiple-trackings.php

Delete create-a-tracking-item.php