Update alpine.md with better info about proxy limitations

The issue described in #1515 is now mentioned in the Alpine documentation so that readers understand why the example does not store the editor as component data and why they should not do so either.

docs/installation/alpine.md

@@ -48,7 +48,7 @@ import StarterKit from '@tiptap/starter-kit'
 
 document.addEventListener('alpine:init', () => {
   Alpine.data('editor', (content) => {
-    let editor
+    let editor // Alpine's reactive engine automatically wraps component properties in proxy objects. Attempting to use a proxied editor instance to apply a transaction will cause a "Range Error: Applying a mismatched transaction", so be sure to unwrap it using Alpine.raw(), or simply avoid storing your editor as a component property, as shown in this example.
 
     return {
       updatedAt: Date.now(), // force Alpine to rerender on selection change