Standardize directory trees in quickstarts

[vcampitelli]

Currently, our quickstarts have directory trees in different locations (and even formats):

1. Ruby on Rails doesn't have it because there are too many files to represent
2. Python Flask has it in the end (before the testing step)
3. Express.js has it in the beginning of the article

We want to make a standard way of doing so across different guides.

[ColinFrick]

I think it makes sense to include a directory tree, if the user has to create most / all of the files himself. F.e. the Angular quick start - similar to Ruby on Rails - will utilize ng new to generate the project directory / files. It's not necessary to include the directory tree, because it should already be correct.

I'd prefer the placement and format of the Express.js article

[vcampitelli]

It seems that Astro has a feature called Project Tree which would be awesome for this