Create generic case studies

Three case studies were created:
* Defend Iceland (presented in a keynot at DrupalCon Barcelona 2024)
* Drupal Steward
* Drupal secures funding from STF

I added photos for all projects and neutral descrioptions.

Testing locally:

Get the latest code for Drupal CMS.

Fetch and install drupal_cms_demo_content → recipe: composer require drupal/drupal_cms_demo_content

Install site using recipe: drush si ../recipes/drupal_cms_demo_content

Updated testing instructions

Testing locally:

1. Install Drupal CMS locally following the instructions in the README.md of the project
2. Require demo content recipe: ddev composer require drupal/drupal_cms_demo_content
3. Re-install with demo content: ddev drush si ../recipes/drupal_cms_demo_content

Tesing using Drupal CMS online demo:

1. Go to https://www.1xinternet.de/en/drupal-cms-start-demo
2. Request demo with demo content (default option)

I have visited /case-studies/transforming-non-governmental-organization-websites-drupal and encountered a Drupal logo underneath the elephant photo. It is most likely the Client logo. However, to the uninitiated this looks like a bug.

Consider either reducing the size of the logo and or making it a logo that looks like an NGO organisation so that it is not visually jarring.