When generating static website custom `theme` does not match `--assets-dir=example-dir`

[faebebin]

example - this does now work: reveal-md my-slides --static=web --theme=example-dir/my-theme.css --assets-dir=example-dir

When using custom theme and --assets-dir together they do not match in the generated html. In index html the css import still points to href=/_assets/example_dir/my-theme.css and returns 404 becuase the file is now at example-dir/my-theme.css