feat(markdown): Initial version for v3 tutorial

markdown/dev/tutorials/pattern-design/our-first-part/en.md

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+---
+title: Your first part
+order: 120
+---
+
+Much like garments themselves, patterns are made up of _parts_.
+Most patterns will have multiple parts. A sleeve, a back part, the collar, and
+so on. Our pattern is very simple, and only has one part: the bib.
+
+It's a good idea to keep each part in its own file. You don't *have to* do
+this, but it's a good habit to get into. When you create more elaborate designs
+with multiple parts, keeping each in its own file makes for a more tidy
+and approachable code base.  
+
+## bib.mjs
+
+The previous step has already set everything up for us. Our design's main file
+lives in `design/src/index.mjs`, and our part lives in `design/src/bib.mjs`.
+
+This `bib.mjs` is where we'll do all our work. It currently looks like this:
+
+```design/src/bib.mjs
+function draftBib({ part }) {
+
+  return part
+}
+
+export const bib = {
+  name: 'tutorial.bib',
+  draft: draftBib,
+}
+```
+
+### The part object
+
+Each part in FreeSewing is an object that describes everything there is to know about the part.
+
+The only mandatory keys on a part object are `name` and `draft`.
+
+<Related>
+Refer to [the part reference documentation](/reference/api/part) for 
+all details about configuring the part object 
+</Related>
+
+#### The part name
+
+```design/src/bib.mjs
+  name: 'tutorial.bib',
+```
+
+A part's `name` should be unique in a pattern. Apart from that, anything goes.
+Although you probably want to give it a sensible name.
+
+As you can see in the example above, we're using `tutorial.bib` as the name.
+
+<Tip>
+We **strongly** recommend to follow this `design.part` naming scheme to avoid
+naming conflicts when mixing parts from various designs to create new designs.
+</Tip>
+
+#### The part's draft method
+
+```design/src/bib.mjs
+  draft: draftBib,
+```
+
+The second mandatory key on the part object is `draft` which should hold the method that drafts the part.
+
+In our example above, it refers to the `draftBib` function we defined at the top of the file.
+For now this function doesn't do much, but that will change soon enough.
+
+<Note> 
+This structure of putting the draft method at the top of the file and
+the part object at the bottom is a bit of a convention in FreeSewing. 
+</Note>
+
+## index.mjs
+
+<Tip>
+Feel free to skip to [Adding
+measurements](/tutorials/pattern-design/adding-measurements) if you're itching
+to get started.  Or, read on for an explanation of what's going on in the
+`index.mjs` file.
+</Tip>
+
+The `index.mjs` file is already complete and we won't be making any changes to
+it.  But for those who are curious about what's going on inside `index.mjs`,
+we're including a version with comments below:
+
+```design/src/index.mjs
+/*
+ * Import the `Design` constructor 
+ * from the FreeSewing core library
+ *
+ * This Design constructor is a method 
+ * (also known as a function) 
+ * that creates a new Design
+ */
+import { Design } from '@freesewing/core'
+/*
+ * Import the `bib` part from the bib.mjs file
+ * in the same folder as this index.mjs file
+ *
+ * This is the part we'll be working on 
+ * in this tutorial
+ */
+import { bib } from './bib.mjs'
+
+/*
+ * Create a new Pattern by passing 
+ * a configuration object
+ * to the Design contructor
+ */
+const Pattern = new Design({
+  /*
+   * This `data` key is optional, but we 
+   * typically add a name and version here
+   */
+  data: {
+    version: "0.0.1",
+    name: "Tutorial",
+  },
+  /*
+   * This `parts` key is the most important thing
+   * It holds a list of `parts` for our Design.
+   * A Pattern/Design is in the end not much more 
+   * than a collection of parts. 
+   */
+  parts: [ bib ],
+})
+
+/*
+ * We are exporting our Pattern
+ * (so others can use it)
+ * but we also (re-)export our bib part
+ * this allows others to re-use it 
+ * in their own designs
+ */
+export { bib, Pattern }
+```