Remove StartType form; Add Twig and Doctrine migrations

.gitignore

composer.json

composer.lock

config/packages/prod/doctrine.yaml

config/packages/test/twig.yaml

public/js/index.js

src/Controller/MainController.php

src/Entity/Topic.php

src/Form/StartType.php

symfony.lock

templates/base.html.twig

templates/index.html.twig