Plugin fails to translate when using regional variants in source language (e.g., zh-hans)

Problem/Motivation

Currently, for source language codes, the module expects ISO 3166-1 alpha-2 codes without regional variants (e.g., zh instead of zh-hans). However, Drupal core often provides language codes with regional variants such as zh-hans or pt-br.

When creating content in Chinese (zh-hans in Drupal) and attempting to translate it into another language, the plugin fails to perform the translation.

Steps to reproduce

1. Create a page in Chinese (zh-hans).
2. Attempt to translate the page into another language.

Proposed resolution

The source language code should be normalized before being used for translation.
Specifically, it should be passed through:
LanguageCode::removeRegionalVariant()