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/pointonline/en.md

@@ -0,0 +1,70 @@
+---
+title: pointOnLine()
+---
+
+```js
+bool utils.pointOnLine(
+  Point from, 
+  Point to, 
+  Point check, 
+  float precision = 1e6
+)
+```
+
+Returns `true` if the point `check` lies on a line segment from point `from` to point `to`.
+
+The fourth parameter controls the precision. See [pointOnBeam](#utilspointonbeam).
+
+<Example part="utils_pointonline" caption="A Utils.pointOnLine() example" />
+
+```js
+let {
+  Point,
+  points,
+  Path,
+  paths,
+  Snippet,
+  snippets,
+  utils
+} = part.shorthand();
+
+points.from1 = new Point(10, 10);
+points.to1 = new Point(90, 60);
+points.from2 = new Point(10, 30);
+points.to2 = new Point(90, 80);
+points.b1 = new Point(170, 110);
+points.b2 = new Point(170, 130);
+
+let scatter = [];
+for (let i = 1; i < 36; i++) {
+  for (let j = 1; j < 27; j++) {
+    scatter.push(new Point(i * 10, j * 10));
+  }
+}
+let snippet;
+for (let point of scatter) {
+  if (utils.pointOnLine(points.from1, points.to1, point)) snippet = "notch";
+  else snippet = "bnotch";
+  snippets[part.getId()] = new Snippet(snippet, point);
+  if (utils.pointOnLine(points.from2, points.to2, point, 0.01)) {
+    snippet = "notch";
+  } else snippet = "bnotch";
+  snippets[part.getId()] = new Snippet(snippet, point);
+}
+paths.line1 = new Path()
+  .move(points.from1)
+  .line(points.to1)
+  .attr("class", "fabric stroke-lg");
+paths.lne1 = new Path()
+  .move(points.to1)
+  .line(points.b1)
+  .attr("class", "fabric dashed");
+paths.line2 = new Path()
+  .move(points.from2)
+  .line(points.to2)
+  .attr("class", "fabric stroke-lg");
+paths.lne2 = new Path()
+  .move(points.to2)
+  .line(points.b2)
+  .attr("class", "fabric dashed");
+```