Make adding pdo_pgsql more prominent

[samdark]

Q	A
Is bugfix?	❌
New feature?	❌
Breaks BC?	❌
Tests pass?	✔️
Fixed issues	-

[Copilot]

Pull request overview

This PR improves the documentation for adding PostgreSQL support to a Yii3 application by making the pdo_pgsql extension installation instructions more prominent and detailed. Instead of just mentioning to add it to the install-php-extensions list, the PR now shows a complete example of what the Dockerfile configuration should look like.

Changes:

• Expanded the Docker setup instructions to include a full dockerfile code block showing all required PHP extensions including pdo_pgsql
• Separated the rebuild command into its own code block with proper shell syntax highlighting for better clarity