docs: clarify use:enhance compatibility with method="POST" (#12546)

* Update 30-form-actions.md

* Update documentation/docs/20-core-concepts/30-form-actions.md

---------

Co-authored-by: Tee Ming <[email protected]>

Author: garysassano

documentation/docs/20-core-concepts/30-form-actions.md

@@ -329,6 +329,8 @@ The easiest way to progressively enhance a form is to add the `use:enhance` acti
 +<form method="POST" use:enhance>
 ```
 
+> `use:enhance` can only be used with forms that have `method="POST"`. It will not work with `method="GET"`, which is the default for forms without a specified method. Attempting to use `use:enhance` on forms without `method="POST"` will result in an error.
+
 > Yes, it's a little confusing that the `enhance` action and `<form action>` are both called 'action'. These docs are action-packed. Sorry.
 
 Without an argument, `use:enhance` will emulate the browser-native behaviour, just without the full-page reloads. It will: