The alternative configuration method for setting the baseUrl is not setting on the link/url structure in sitemap.xml

[Darren-Caboz]

To Reproduce

Step by step instructions to reproduce the behavior:

1. Setting the baseUrl using the alternative configuration method as explain per guide: https://github.com/apostrophecms/apostrophe-site-map/#alternative-configuration
2. Loading http://localhost:3000/sitemap.xml - The baseUrl is not showing on the links
3. Have also run node app apostrophe-site-map:clear as well and reimplemented steps 1 and 2

Expected behavior

When applying the baseUrl in the 'apostrophe-site-map' as option, it should be include in the sitemap.xml generated as part of the links/url structure. For eg 0.9 daily http://localhost:3000/about-us

Describe the bug

When applying the baseUrl in the 'apostrophe-site-map' as option (as per https://github.com/apostrophecms/apostrophe-site-map/#alternative-configuration), it should be included in the sitemap.xml as part of the links/url structure.
for eg 0.9 daily /about-us

Details

Version of Node.js:
v8.11.4

Server Operating System:
MacOS Mojave

Additional context:

When using the main baseUrl configuration, it does prepend the baseUrl to the links/url in the sitemap.xml - for eg 0.9 daily http://localhost:3000/about-us