docs: v13 docs & migration guide (#1709)

Author: mdjastrzebski

website/docs/12.x/docs/api/misc/async.mdx

@@ -0,0 +1 @@
+["v13", { "type": "dir", "name": "previous", "label": "Previous versions", "collapsed": true }]

website/docs/12.x/docs/api/misc/config.mdx

@@ -0,0 +1 @@
+["v12", "jest-matchers", "v11", "v9", "v7", "v2"]

website/docs/12.x/docs/api/misc/other.mdx

@@ -19,7 +19,7 @@ export default defineConfig({
   },
   multiVersion: {
     default: '12.x',
-    versions: ['12.x', '13.x-alpha'],
+    versions: ['12.x', '13.x-next'],
   },
   route: {
     cleanUrls: true,