Built-in venv manager should detect `.py` files with inline metadata, add them as projects.

[karthiknadig]

[1994-371174]

https://github.com/microsoft/vscode-python-environments/issues/136https://github.com/github-linguist/linguist.git

[1994-371174]

২৮,৫১০,২৪৯

[eleanorjboyd]

Stella Huang (@StellaHuang95) thinking you could work on this as it would be a part of beginning to support PEP723

[StellaHuang95]

See #1602 for the progress.