[gatsby-theme-minimal-blog]: footnotes do not render

[sparky005]

Description

Using the gatsby-theme-minimal-blog theme, using footnotes does not seem to work. The footnotes are just rendered as regular text, eg:

Here's a simple footnote,[^1] and here's a longer one.[^bignote]

[^1]: This is the first footnote.

[^bignote]: this is a longer footnote, but not that much longer

Steps to reproduce

Clear steps describing how to reproduce the issue. Please please please link to a demo project if possible, this makes your issue much easier to diagnose (seriously).

1. create a new page from the starter with npx gatsby new gatsby-starter-minimal-blog https://github.com/LekoArts/gatsby-starter-minimal-blog
2. add or edit a post to use footnotes

Example project: https://elaborate-paletas-85fd95.netlify.app/markdown-reference
Source: https://github.com/sparky005/gatsby-minimal-demo/blob/main/content/posts/markdown-reference/index.mdx

Expected result

Footnotes are rendered correctly, as shown here: #726 (comment)

Actual result

They do not render correctly, as shown above

Environment

Run gatsby info --clipboard in your project directory and paste the output here.

System:
OS: macOS 13.1
CPU: (8) x64 Intel(R) Core(TM) i7-1068NG7 CPU @ 2.30GHz
Shell: 5.8.1 - /bin/zsh
Binaries:
Node: 19.2.0 - /usr/local/bin/node
Yarn: 3.3.0 - ~/.asdf/shims/yarn
npm: 8.19.3 - /usr/local/bin/npm
Languages:
Python: 3.9.13 - /Users/asadik/.asdf/shims/python
Browsers:
Chrome: 108.0.5359.124
Firefox: 104.0.2
Safari: 16.2