add support for `base` option

[hadfieldn]

Eric, thanks for providing this utility. Unfortunately it seems to assume that all components are located in the same folder, as it failed to include components referenced by my main component that were located in other folders. I modified it to allow for a base path argument to use as a base for relative URLs, and this seems to have solved the issue.

Of course it's very possible that I'm doing something wrong or that there's a better way of solving the problem.

[ebidel]

@hadfieldn Thanks for this. Sorry for the delay.

If you run the script in your app's directory, does it work? Just curious.

Still seems like a good option to add.