fix(markdown): Don't use MDX components to construct headers

Closes #4776

This is a somewhat low-tech fix for this problem.
That's because it's not entirely trivial to resolve this as the MDX
components rely on the React context to figure out the title of the
page, but the remark plugin runs in an SSR context and does not have
access to the React contenxt.

Futhermore, while we could load the context statically for dev (given
the navigation context for the docs is availabel in the prebuild data)
this would lead to problems for org because we don't know inside this
remark plugin what language the user requested.

And while I'm certain we could figure it out given enough effort, it
hardly seems worth is since this is used in very few places.

In addition, it would do nothing to solve the matter of the nested a
tags when putting a link in the title, which clashes with the
auto-generated amchor links for titles.

So new rules:

- Title cannot be a link
- You can not use `DocsTitle` as title

markdown/dev/design/en.md

@@ -5,79 +5,90 @@ title: Design
 If you are looking to use FreeSewing to design parametric sewing patterns,
 below are the most relevant materials on this site for you: 
 
-## [<DocsTitle slug="guides/prerequisites" />](/guides/prerequisites)
+## Before you start
 
 Outlines the minimal prerequisites you should understand before you dive in, including:
 
+- <DocsLink slug="guides/prerequisites" />
 <ReadMore root="guides/prerequisites" />
 
-## [<DocsTitle slug="guides/best-practices" />](/guides/best-practices)
+## Pattern design best practices
 
 In design as in code, there's often many different ways to accomplish the same
 result.  We have a list of best practices that we recommend you follow. Even if
 in the end you make your own choices, we recommend you at least ready through
 them once. They include:
 
+- <DocsLink slug="guides/best-practices" />
 <ReadMore root="guides/best-practices" />
 
-## [<DocsTitle slug="guides/designs" />](/guides/designs)
+## Design guide
 
 We've so far been talking about *patterns* but what you're really be creating is a *design*.
 What the difference is, and what goes into a design to generate a pattern is explained in our design guide:
 
+- <DocsLink slug="guides/designs" />
 <ReadMore root="guides/designs" />
 
-## [<DocsTitle slug="tutorials/pattern-design" />](/tutorials/pattern-design)
+## Pattern design tutorial
 
 This is our pattern design tutorial. If you're new to designing patterns with
 FreeSewing, following the tutorial is the fastest way to get started:
 
-<ReadMore root="tutorials/pattern-design" />
+- <DocsLink slug="tutorials/pattern-design" />
+<ReadMore root="tutorials/pattern-design" recurse />
 
-## [<DocsTitle slug="guides/plugins" />](/guides/plugins)
+## Plugin guide
 
 FreeSewing can be extended with plugins. We provide a range of plugins that you can use.
 However, if you'd like to write your own plugins, you should also read the guide on how they work:
 
+- <DocsLink slug="guides/plugins" />
 <ReadMore root="guides/plugins" />
 
-## [<DocsTitle slug="howtos/design" />](/howtos/design)
+## Common design challenges
 
 This is a list of common challenges in designing parametric sewing patterns, and tips on how to tackle them:
 
+- <DocsLink slug="howtos/design" />
 <ReadMore root="howtos/design" />
 
-## [<DocsTitle slug="howtos/code" />](/howtos/code)
+## Common code challenges
 
 While designing patterns in code has a lot of benefits, there might be times
 where things that are intuitive on paper don't come naturally to you.  This is
 a list of common code challenges and how to tackle them:
 
+- <DocsLink slug="howtos/code" />
 <ReadMore root="howtos/code" />
 
-## [<DocsTitle slug="reference/api" />](/reference/api)
+## Core API
 
 This is the reference documentation for FreeSewing's core library. 
 This is where you can look up every possible API call with examples:
 
+- <DocsLink slug="reference/api" />
 <ReadMore root="reference/api" />
 
-## [<DocsTitle slug="reference/macros" />](/reference/macros)
+## Macros
 
 This is the reference documentation for macros provided by FreeSewing's own plugins:
 
+- <DocsLink slug="reference/macros" />
 <ReadMore root="reference/macros" />
 
-## [<DocsTitle slug="reference/snippets" />](/reference/snippets)
+## Snippets
 
 This is the reference documentation for snippets provided by FreeSewing's own plugins:
 
+- <DocsLink slug="reference/snippets" />
 <ReadMore root="reference/snippets" />
 
-## [<DocsTitle slug="reference/plugins" />](/reference/plugins)
+## Plugins
 
 This is the list of all plugins we provide:
 
+- <DocsLink slug="reference/plugins" />
 <ReadMore root="reference/plugins" />
 
 <Note>