Add action docs on multiple actions (#10527)

Author: brophdawg11

docs/route/action.md

@@ -129,6 +129,62 @@ You can `throw` in your action to break out of the current call stack (stop runn
 
 For more details and expanded use cases, read the [errorElement][errorelement] documentation.
 
+## Handling multiple actions per route
+
+A fairly common question that pops up is _"What if I need to handle multiple different behaviors in my action?"_ There's a few ways to accomplish this, but usually the simplest is to put a `name`/`value` on your `<button type="submit">` and use that in the action to decide which code to execute (that's right - submitting [buttons][button] can have name/value attributes!):
+
+```jsx lines=[3,5,10,30-32,42-44]
+async function action({ request }) {
+  let formData = await request.formData();
+  let intent = formData.get("intent");
+
+  if (intent === "edit") {
+    await editSong(formData);
+    return { ok: true };
+  }
+
+  if (intent === "add") {
+    await addSong(formData);
+    return { ok: true };
+  }
+
+  throw json(
+    { message: "Invalid intent" },
+    { status: 400 }
+  );
+}
+
+function Component() {
+  let song = useLoaderData();
+
+  // When the song exists, show an edit form
+  if (song) {
+    return (
+      <Form method="post">
+        <p>Edit song lyrics:</p>
+        {/* Edit song inputs */}
+        <button type="submit" name="intent" value="edit">
+          Edit
+        </button>
+      </Form>
+    );
+  }
+
+  // Otherwise show a form to add a new song
+  return (
+    <Form method="post">
+      <p>Add new lyrics:</p>
+      {/* Add song inputs */}
+      <button type="submit" name="intent" value="add">
+        Add
+      </button>
+    </Form>
+  );
+}
+```
+
+If a button name/value isn't right for your use case, you could also use a hidden input to send and `intent` or you could submit different HTTP methods via the [`<Form method>`][form-method] prop (`POST` for add, `PUT`/`PATCH` for edit, `DELETE` for remove).
+
 [loader]: ./loader
 [pickingarouter]: ../routers/picking-a-router
 [dynamicsegments]: ./route#dynamic-segments
@@ -146,3 +202,5 @@ For more details and expanded use cases, read the [errorElement][errorelement] d
 [useactiondata]: ../hooks/use-action-data
 [returningresponses]: ./loader#returning-responses
 [createbrowserrouter]: ../routers/create-browser-router
+[button]: https://developer.mozilla.org/en-US/docs/Web/HTML/Element/button
+[form-method]: ../components/form#method