Support basePath in Nextjs

[khalil-omer]

As described in this issue in sst/sst and as addressed in this sst/sst PR, if basePath is set in next.config.js, sst/ion ignores that path when defining Cloudfront routes, so Next expects assets at /basepath/_next/foo but Cloudfront is serving them at _next/foo.

[fwang]

Update release v0.0.147 with OpenNext 3.0.0-rc.8. basePath should now be supported.

Feel free to re-open this if still not supported.

[khalil-omer]

@fwang thanks, I agree this is fixed as far as routing, but seeing one bug with next/image. I'll open an issue in the open-next repo.

With 'app' as the basePath, This URL is attempted to be fetched but fails:

/app/_next/image?url=%2Fsplash-screen-icon.png&w=96&q=75

This is the correct URL that should be fetched, which works:

/app/_next/image?url=%2Fapp%2Fsplash-screen-icon.png&w=96&q=75