add a stub guide for custom adapters

packages/docs/src/guides/custom-adapters.md

@@ -0,0 +1,10 @@
+---
+title: Custom Adapters
+description: Adapting Reacord to another Discord library
+---
+
+# Custom Adapters
+
+Reacord's core is built to be library agnostic, and can be adopted to libraries other than Discord.js. However, Discord.js is the only built-in adapter at the moment, and the adapter API is still a work in progress.
+
+If you're interested in creating a custom adapter, [see the code for the Discord.js adapter as an example](https://github.com/itsMapleLeaf/reacord/blob/main/packages/reacord/library/core/reacord-discord-js.ts). Feel free to [create an issue on GitHub](https://github.com/itsMapleLeaf/reacord/issues/new) if you run into issues.

packages/docs/src/guides/select-menu.md

@@ -1,4 +1,5 @@
 ---
+order: 4
 title: Select Menus
 description: Using select menu components
 ---