NextjsServerOverrides.nextjsBucketDeploymentProps should be typed as optional

[zmillman]

This line: https://github.com/jetbridge/cdk-nextjs/blob/d669ff82788e081ff9ddc1a2b2a703979346fc19/src/NextjsServer.ts#L22

As a result, I have to add a no-op nextjsBucketDeploymentProps: {}

  const next = new Nextjs(this, "Nextjs", {
    nextjsPath: ".",
    overrides: {
      nextjsServer: {
        functionProps: {
          // ...
        },
        // Fix typechecking error (this should be optional but isn't)
        nextjsBucketDeploymentProps: {},
      },
    },
  });