docs: mention that postgres is required to run the generator (#457) #1082

Job	Run time
test	18s
test_generated_apps (defaults, ackama_rails_template.config.yml, --skip-javascript)	5m 26s
test_generated_apps (all, ci/configs/all.yml, --skip-javascript)	5m 53s
test_generated_apps (all-typescript, ci/configs/all-typescript.yml, --skip-javascript)	9m 2s
test_generated_apps (basic, ci/configs/basic.yml, --skip-javascript)	3m 37s
test_generated_apps (basic-typescript, ci/configs/basic-typescript.yml, --skip-javascript)	4m 26s
test_generated_apps (github_actions, ci/configs/github_actions.yml, --skip-javascript)	3m 52s
test_generated_apps (react, ci/configs/react.yml, --skip-javascript)	4m 30s
test_generated_apps (react-typescript, ci/configs/react-typescript.yml, --skip-javascript)	4m 58s
test_generated_apps (sidekiq, ci/configs/sidekiq.yml, --skip-javascript)	4m 35s
test_generated_apps (devise, ci/configs/devise.yml, --skip-javascript)	4m 30s
test_generated_apps (basic_with_skips, ci/configs/basic.yml, --skip-spring --skip-javascript)	4m 30s
test_generated_apps (bootstrap, ci/configs/bootstrap.yml, --skip-javascript)	3m 57s
test_generated_apps (bootstrap-typescript, ci/configs/bootstrap-typescript.yml, --skip-javascript)	5m 40s
test_generated_apps (capistrano, ci/configs/deploy_with_capistrano.yml, --skip-javascript)	3m 45s
test_generated_apps (ackama_ec2_capistrano, ci/configs/deploy_with_ackama_ec2_capistrano.yml, --s...	5m 48s
	1h 14m 47s

Provide feedback