Provide Platform.sh configuration files.

[GuGuss]

• [x] Add the 2 missing files: services.yaml & settings.php required by Platform.sh (read-only filesystem). See example here.

[GuGuss]

• [x] Currently getting a:

Warning: file_put_contents(sites/default/settings.php): failed to open stream: Read-only file system in drupal_rewrite_settings() (line 337 of core/includes/install.inc).
drupal_rewrite_settings(Array)
install_write_profile(Array)
install_run_task(Array, Array)
install_run_tasks(Array)
install_drupal(Object)

[GuGuss]

• [ ] Stop hardcoding $settings['hash_salt']. Include this: Drupal\Component\Utility\Crypt.