chore(markdown): Restructuring dev docs

markdown/dev/reference/api/settings/sa/en.md

@@ -0,0 +1,22 @@
+--- 
+title: sa
+---
+
+The seam allowance in mm.
+
+Not setting this, setting it to `false`, or to zero, will draft a pattern without seam allowance.
+
+
+```js
+import brian from "@freesewing/brian";
+
+let pattern = new brian({
+  sa: 10
+})
+```
+
+<Note>
+
+This is ignored if [settings.complete](#complete) is `false`
+
+</Note>