feat: Flat import of markdown repo

This is a flat (without history) import of (some of) the content
from our markdown module.

We've imported this without history because the repo contains our
blog posts and showcases posts content prior to porting them to strapi.

Since this contains many images, it would balloon the size of this repo
to import the full history.

Instead, please refer to the history of the (archived) markdown repo
at: https://github.com/freesewing/markdown

markdown/dev/reference/macros/rmd/en.md

@@ -0,0 +1,30 @@
+---
+title: rmd
+---
+
+The `rmd` macro removes a dimension.
+It is provided by the [dimension plugin](/reference/plugins/dimension/).
+
+To be able to use this plugin, you need to give your dimension an id:
+
+```js
+macro('ld', {
+  from: points.from,
+  to: points.to,
+  d: 0,
+  id: 'example'
+})
+```
+
+Now you can remove it as such:
+
+```js
+macro('rmd', {
+  id: 'example'
+})
+```
+
+| Property | Default | Type     | Description | 
+|----------|---------|----------|-------------|
+| `id`     |         | `string` | The id of the dimension to remove |
+