In this example, we'll set up a form action to create a simple subscription form.
Actions are exported from the +page.server.js file. Actions have access to the form data passed through the request.
Actions can be called through forms in Svelte components. When calling the the default action of a page, an action attribute is not required.
Actions can be named to support multiple actions from the same endpoint.
To call a named action, specify it in the query string of the form's action URL.