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/pd/en.md

@@ -0,0 +1,35 @@
+---
+title: pd
+---
+
+The `pd` macro adds a *path dimension* to your pattern, indicating the length of a path.  
+It is provided by the [dimension plugin](/reference/plugins/dimension/).
+
+<Example part="path_length" caption="Example of a multiple path dimensions" />
+
+```js
+macro('pd', {
+  path: paths.example,
+  d: -20
+})
+```
+
+| Property        | Default | Type                | Description | 
+|----------------:|---------|---------------------|-------------|
+| `path`          |         | [Path](/reference/api/path)   | The path to draw the dimension along |
+| `offset`        | 0       | Number              | The offset at which to draw the dimension |
+| `text`          | Path length | Number          | The text to go on the dimension if not the length of the path |
+| `id`            | auto-assigned | String | A custom ID under wich paths and points will be created |
+| `noStartMarker` | `false` | Boolean             | Whether to not draw a start marker |
+| `noEndMarker`  | `false` | Boolean             | Whether to not draw an end marker |
+
+<Note>
+
+Setting a custom ID will:
+
+ - Allow removal of the dimension with [the `rmd` macro](/reference/macros/rmd)
+ - Prevent removal of the dimension with [the `rmad` macro](/reference/macros/rmad/) 
+
+</Note>
+
+