Document keepalive in quickstart example

[cseas]

I've used the JavaScript quickstart document to setup Segment using the snippet.

How do I setup keepalive in the same to make sure Segment requests complete before a redirection happens?

The docs just mention a link to this comment which doesn't clearly explain how keepalive is supposed to be used when Segment is installed via snippet.

[silesky]

@cseas Thanks for the feedback! There are two slightly-different APIs (not my decision).

The snippet is:

   const analytics = analytics.load('<MY_WRITEKEY>',  // first argument is string, not object
      {
        integrations: {
          'Segment.io': {
            deliveryStrategy: {
              config: {
                keepalive: true,
              },
            },
          },
        },
      }
    )