add .devcontainer setup #262

similar to this:
https://github.com/scicloj/devcontainer-templates/tree/main/src/scicloj

(not needed things can be removed, if needed)

->
Makes hacking on libpython-clj a bit easier.

The setup as well be re-used for a test suite with GitHub actions.
But not sure it would simplify this a lot:
https://github.com/clj-python/libpython-clj/blob/master/.github/workflows/test.yml

Devcontainer have different "philosophy". Instead of testing all JDKs, we "freeze to one".

See here for reference:
https://github.com/scicloj/clojisr/blob/master/.github/workflows/ci.yml

The tests run "inside" the same devcontainer setup then the "project" has.