Support fallback and other objects under rewrites in next config.

[jsmittyTrails]

In the next configuration rewrites are not just arrays but also objects in the latest versions. When adding fallbacks in the rewrites and running tf-next build you end up with an error.

Example of a fallback rewrite:

async rewrites() {
    return {
      fallback: [
        {
          source: '/:path*',
          destination: `${host}/:path*`,
        },
        {
          source: '/:locale*/:path*',
          destination: `${host}/:path*`,
          locale: false,
        },
      ],
    }
  },

This ultimately results in an error because the return is not an array but an object:

TypeError: e.map is not a function
    at convertRewrites (/opt/homebrew/lib/node_modules/tf-next/node_modules/@millihq/tf-next-runtime/dist/index.js:1:162099)
    at build (/opt/homebrew/lib/node_modules/tf-next/node_modules/@millihq/tf-next-runtime/dist/index.js:33:145798)
    at async buildCommand (/opt/homebrew/lib/node_modules/tf-next/dist/commands/build/build.js:132:29)
    at async Object.createBuildCommand.withApiService [as handler] (/opt/homebrew/lib/node_modules/tf-next/dist/commands/build/build.js:203:5)
    ```