Add Symfony Example

[geerlingguy]

Symfony is a PHP framework for web projects.

I'd like to add an example that builds a generic 'hello-world' Symfony app and connects to SQLite in a separate container.

One interesting aspect (and one about which I wrestle with in the 'this-isn't-something-for-prod-therefore-why-is-it-done-in-acontainer' way) is the idea of doing Composer work inside Docker.

IMO, it would be better to do all the app build process in a separate pipeline, then run the app in Docker containers. Technically the build process could be managed in some Docker containers... but you should always run your app in the exact same way as Production. And Production should not have Composer, nor should it be involved in your build process (especially since that saps up resources!).