Document .torchxconfig behavior in home directory

[d4l3k]

📚 Documentation

Link

https://pytorch.org/torchx/main/runner.config.html

Context: https://fb.workplace.com/groups/140700188041197/posts/326515519459662/?comment_id=328106399300574&reply_comment_id=328113552633192

What does it currently say?

The CLI only picks up .torchxconfig files from the current-working-directory (CWD) so chose a directory where you typically run torchx from.

What should it say?

It should explain how it can also be read from home and how the options are merged together.

Why?

Behavior is unclear to users.

[d4l3k]

@kiukchung Do we have TORCHXCONFIG env variable documented as well?

[kiukchung]

We could definitely do better. The TORCHXCONFIG env var is documented as part of the torchx.runner.config.find_configs() method pydocs, but it won't be obvious to the user looking at the top level config documentation. We should mention it in the module level docs here