Update versioning.mdx

editing the versions documentation to reflect the new feature mentioned here:
https://app.plain.com/workspace/w_01H3FZJ8MG74GFXA5WA3MPB446/thread/th_01J8072V8GHJ17KYP2B1SNHGJX/

Author: dino475

settings/versioning.mdx

@@ -10,6 +10,17 @@ These guides will assume `v1` pages are in a folder named `v1`, `v2` pages are i
 
 Add `"versions": ["v2", "v1"]` to your `mint.json` file where `v1` and `v2` are the names of your versions. You can put any number of versions in this array. The first version from the array serves as the default version.
 
+If you would like to specify a default version, you can do so like this:
+
+```
+"versions": [
+{
+  name: "name",
+  default: true
+}
+]
+```
+
 <Tip>
   The versions dropdown will show your versions in the order you include them in
   `mint.json`.