Improve devcontainer experience by linking sample config as real config

.devcontainer/postCreateCommand.sh

@@ -1,5 +1,6 @@
 #!/bin/sh
 
+ln -s ./conf.sample.php cfg/conf.php
 composer install --no-dev --optimize-autoloader
 sudo chmod a+x "$(pwd)" && sudo rm -rf /var/www/html && sudo ln -s "$(pwd)" /var/www/html
 npm install --global nyc