feat: add Alpine based Docker image (#43)
* Gitignore .idea folder (PhpStorm etc)
* Alpine version of Dockerfile
* Bake definition to build Docker images
* Docs for Docker image building
* Link to docker.md
* Use latest change on using official php-src repo and PHP-8.2 branch
* Remove ARGS and get other changes from Dockerfile (original)
* Update GHA workflows with Dockerfile.alpine
