Create an SDW-compatible config.json file on disk when using make dev-tor

[zenmonkeykstop]

Description

Currently, the dev env output includes a JSON snippet that can be used to set up SecureDrop Workstation for testing purposes. To make it easier to do so, the JSON could be written to a file instead. Said file's path/name should be included in .gitignore.

How will this impact SecureDrop users?

Improved developer experience.

How would this affect SecureDrop's threat model?

No impact.

User Stories

As a developer, I want to be able to set up SDW with a dev SD env with ease and haste.