What is the default value for a plugin's `sortOrder`?

### Is there an existing issue for this?

- [X] I have searched the existing issues

### What's missing?

In [src/pages/development/components/plugins.md](https://github.com/AdobeDocs/commerce-php/blob/c70d9497d1362c5ec7756836acacaa66681c7355/src/pages/development/components/plugins.md?plain=1#L29-L50), it says:

> The following elements are optional:
>
> * `plugin sortOrder`. Plugins that call the same method run them using this order.
> * `plugin disabled`. To disable a plugin, set this element to `true`. The default value is `false`.

What is the default value for `sortOrder`?

Start with src/pages/development/components/plugins.md, especially the optional plugin elements section linked in the issue. Verify the default sortOrder from an authoritative project source, then document it alongside the existing disabled default; the documentation is done when the value and its ordering behavior are explicit.

Written by the indexing model from the issue text.