Drupal 11 compatibility fixes for select_text_value

Problem/Motivation

We are using the select_text_value module on several of our websites that we want to migrate to Drupal 11.

Proposed resolution

• Implement a Drupal 11 compatible version of this module.
• Enable Gitlab CI.
• Fix phpcs, phpstan and cspell warnings.
• Add composer.json and README.md files.

This MR also includes a small fix to better handle key|label values.

Has been successfully tested on Drupal 11.0.5 PHP 8.3.

Remaining tasks

Publish, review and validate MR.

Testing on Drupal 11

To test on Drupal 11, add the following lines to your composer.json repositories section:

  "repositories": [
    {
      "type": "vcs",
      "url": "https://git.drupalcode.org/issue/select_text_value-3479459.git"
    },

and then run:

composer require drupal/select_text_value:dev-3479459-drupal-11-compatibility