All subsection links are broken in the FHIR Server User's Guide

[lmsurpre]

Describe the bug
I think our site builder used to create section links like #21-installing-a-new server for a section title like 2.1 Install a new server.
Now it produces #2.1-installing-a-new-server and so all the links to sections with a . in them are broken.

To Reproduce
Steps to reproduce the behavior:

1. Go to https://ibm.github.io/FHIR/guides/FHIRServerUsersGuide
2. Try clicking a link for one of the subsections (e.g. 2.1)

Expected behavior
All links work

Additional context
Maybe our site changed when we upgraded version of Gatsby?
I like that these links work in github (e.g. see https://github.com/IBM/FHIR/blob/master/docs/src/pages/guides/FHIRServerUsersGuide.md#21-installing-a-new-server ) and so I'd prefer to update our site builder to generate the section sublinks in the same way that github does it.

[prb112]

I'm pretty sure I know where it's coming from it gatsby-config.js (I think we can easily change)