[docs] Add a warning about the issue with overwriting defaults (#256)

Author: x0k

.changeset/funky-pigs-trade.md

@@ -0,0 +1,5 @@
+---
+"docs2": patch
+---
+
+Add a warning about the issue with overwriting defaults

apps/docs2/src/content/docs/guides/reusable-defaults.mdx

@@ -16,6 +16,15 @@ resolver, theme, validator, merger and translation.
 
 And use it like this:
 
+:::caution
+
+At the moment, Svelte has an [issue](https://github.com/sveltejs/svelte/issues/17220)
+with overwriting module properties during SSR.
+As a workaround, you can use a shallow clone or `export const defaults = { ... }`
+in a `defaults` file.
+
+:::
+
 ```typescript
 import * as defaults from '$lib/form/defaults'