Provide a devcontainer setup for Fauxton

[Stwissel]

Fauxton depends on CouchDB (and eventually an IdP) to work. This suggests a .devcontainer makes sense. Proposed features:

• runs Fauxton
• runs CouchDB
• optional, based on an .env variable runs keycloak as IdP
• CouchDB & keycloak are fully transient, clean on each start
• Scripts initialize keycloak and CouchDB to a known state

If that's acceptable (please comment) I will provide an implementation in a PR

[Stwissel]

I started working on it and have questions:

• for a future IdP support I configure sn epidermal Keycloak instance. Should it start automatically (easy to setup) or only on on demand using a shell script?
• What VSCode plugins are considered essential and which ones a big no-no

if you want to peek: https://github.com/beyonddemise/couchdb-fauxton/tree/fauxton-dev-container