Implement the equivalent of process.env

[lastmjs]

Azle now has a process.env object with the environment variables specified by the developer in the env property of their dfx.json file. Kybra should have the equivalent of this, and the reference section of the Kybra book should be updated accordingly.

[lastmjs]

Actually let's hold off on this while I do the wasi stuff. If we can compile Kybra to wasi, we might have a lot of this done/a better way of doing this

[lastmjs]

os.environ.get looks like the API we should use. I believe if ic-wasi-polyfill had implemented the environment variable imports, then this would work, but I wonder if it will take some more effort on DFINITY's side. We could possibly fork ic-wasi-polyfill and get this working now, but I'm holding off to wait for a better solution.

[lastmjs]

import os


@update
def test() -> str:
    return os.environ.get("TEST_KEY") or "could not find TEST_KEY"