feat(docs): add new recipes section

Recipes document distinct functionality provided by novel use of
existing config, features, and behaviors.

n.b. All pages are currently only placeholders. All names are tentative.

docs/sidebars.js

@@ -43,6 +43,13 @@ module.exports = {
       "behaviors/backlight",
       "behaviors/power",
     ],
+    Recipes: [
+      "recipes/adjust-layer",
+      "recipes/callum-mods",
+      "recipes/home-row-mods",
+      "recipes/multiple-base-layers",
+      "recipes/os-profile-layer",
+    ],
     Codes: [
       "codes/index",
       "codes/keyboard-keypad",