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/path/shiftalong/en.md

@@ -0,0 +1,52 @@
+---
+title: shiftAlong()
+---
+
+```js
+Point path.shiftAlong(float distance[, int stepsPerMm=25])
+```
+
+Returns a point that lies at distance travelled along the path.
+
+<Example part="path_shiftalong" caption="Example of the Path.shiftAlong() method" />
+
+```js
+let { Point, points, Path, paths, Snippet, snippets } = part.shorthand();
+
+points.A = new Point(45, 60);
+points.B = new Point(10, 30);
+points.BCp2 = new Point(40, 20);
+points.C = new Point(90, 30);
+points.CCp1 = new Point(50, -30);
+
+paths.example = new Path()
+  .move(points.A)
+  .line(points.B)
+  .curve(points.BCp2, points.CCp1, points.C);
+
+points.x1 = paths.example
+  .shiftAlong(20)
+  .attr("data-text", "2cm")
+  .attr("data-text-class", "center fill-note")
+  .attr("data-text-lineheight", 6);
+points.x2 = paths.example
+  .shiftAlong(90)
+  .attr("data-text", "9cm")
+  .attr("data-text-class", "center fill-note")
+  .attr("data-text-lineheight", 6);
+
+snippets.x1 = new Snippet("notch", points.x1);
+snippets.x2 = new Snippet("notch", points.x2);
+```
+
+<Note>
+
+##### The second parameter is optional
+
+The second parameter controls the precision by which the path will be *walked*.
+By default, we'll divide it into 25 steps per mm.
+
+If you don't need that precision, you can pass a lower number.
+But for most cases, you can just ignore it.
+
+</Note>