Adding a collect command to copy static assets (including from nested blueprints) to a target dir

[mattaw]

[Briefly discussed here :https://github.com//pull/35#issuecomment-1546711780]

My workflow is:

1. webpack to compile and bundle js and css (Tailwind) into my flask app's static folder.
2. flask digest compile to create md5 tagged and compressed versions

In production the static assets are served by Apache / Nginx. However blueprints and nested blueprints present an annoyance, as their static assets (and their md5 + compressed counterparts) are scattered in directories through my app's source tree.

I would like to reproduce the directory tree from the Flask app source tree with only the static assets and their md5 + compressed versions in it to a target directory of my choice so I can simplify the configuration of Apache/Nginx down to serving one directory tree vs. one per blueprint. This may involve some complexity or similar to create a single manifest.