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/howtos/code/extend-pattern/en.md

@@ -0,0 +1,88 @@
+---
+title: Create a new design based on an existing design
+for: developers
+about: Shows how to create a variation of a pre-existing design
+---
+
+<Note>
+
+##### See this example in our source code
+
+ - [packages/aaron/config/index.js](https://github.com/freesewing/freesewing/blob/72f34101792bda4d8e553c3479daa63cb461f3c5/packages/aaron/config/index.js#L34)
+ - [packages/aaron/src/index.js](https://github.com/freesewing/freesewing/blob/72f34101792bda4d8e553c3479daa63cb461f3c5/packages/aaron/src/index.js#L2)
+ - [packages/carlita/src/index.js](https://github.com/freesewing/freesewing/blob/8474477911daed3c383700ab29c9565883f16d66/packages/carlita/src/index.js#L25)
+
+</Note>
+
+The example below is from Aaron, which is based on Brian.
+
+Brian has a part called `base` that is hidden by default.
+We will use this part as a dependency, and also hide it.
+
+This is what it looks like in the Aaron config file:
+
+```js
+  dependencies: {
+    front: 'base',
+    back: 'front'
+  },
+  inject: {
+    front: 'base',
+    back: 'front'
+  },
+  hide: ['base'],
+```
+
+And here is the code:
+
+```js
+import freesewing from '@freesewing/core'
+import Brian from '@freesewing/brian'
+import plugins from '@freesewing/plugin-bundle'
+import config from '../config'
+// Parts
+import draftBack from './back'
+import draftFront from './front'
+
+// Create design
+const Pattern = new freesewing.Design(config, plugins)
+
+// Attach draft methods to prototype
+Pattern.prototype.draftBase = function(part) {
+  // Getting the base part from Brian
+  return new Brian(this.settings).draftBase(part)
+}
+Pattern.prototype.draftFront = part => draftFront(part)
+Pattern.prototype.draftBack = part => draftBack(part)
+
+export default Pattern
+```
+
+If you have a lot of parts to inherit, you can create a loop like in this
+example from Carlita:
+
+```js
+// Attach draft methods from Carlton to prototype
+for (let m of [
+  'draftBack',
+  'draftTail',
+  'draftTopSleeve',
+  'draftUnderSleeve',
+  'draftBelt',
+  'draftCollarStand',
+  'draftCollar',
+  'draftCuffFacing',
+  'draftPocket',
+  'draftPocketFlap',
+  'draftPocketLining',
+  'draftChestPocketWelt',
+  'draftChestPocketBag',
+  'draftInnerPocketWelt',
+  'draftInnerPocketBag',
+  'draftInnerPocketTab'
+]) {
+  Pattern.prototype[m] = function(part) {
+    return new Carlton(this.settings)[m](part)
+  }
+}
+```