chore(markdown): Move non-api docs to reference

markdown/dev/reference/snippets/bnotch/en.md

@@ -0,0 +1,14 @@
+---
+title: bnotch
+---
+
+The `bnotch` snippet is intended for notches at the back, or when you
+need an alternative to the default `notch`.
+
+It is provided by [plugin-notches](/reference/plugins/notches/).
+
+```js
+snippets.demo = new Snippet('bnotch', points.anchor)
+```
+
+<Example part="snippets_bnotch">An example of the bnotch snippet</Example>