Port backend & frontend README

Refs https://redmine.teklia.com/issues/8008

We need a single source of information for new developers: the doc website is the reference. We shouldonly have links in README towards the online doc (same as on callico repo)

We'll create a new doc page develop/tooling that describes all the complementary actions:

• a section for the frontend with common operations & linting
  • Dev setup is already [ported )(https://doc.arkindex.org/develop/setup/#run-the-frontend)
  • A link towards the new page should be added there
• a section for the backend with:
  • dockerized stack
  • local image server
  • makefile
  • code validation
  • debugging
  • I'm not sure that async tasks list & metrics are that useful.
  • no need to port the migration from archi repo