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/api/utils/stretchtoscale/en.md

@@ -0,0 +1,18 @@
+---
+title: stretchToScale()
+---
+
+```js
+float utils.stretchToScale(float stretch)
+```
+
+The way people measure stretch intuitively is different from the way we handle stretch in code.
+
+When people say *25% stretch* they mean that 10cm fabric gets stretched to 12.5cm fabric.
+In code and on our patterns, that means we need to scale things by 80%.
+
+This method does that by returning:
+
+```js
+1 / (1 + parseFloat(stretch));
+```