variable to get the current folder name

Hi,

Is there a way or variable to get the folder name of the running devcontainer.json (after selecting "Reopen in Container" in VSCode)?

My setup is:
```
repo
.devcontainer/
container1/
devcontainer.json
container2/
devcontainer.json
```
I need to obtain "container1" or "container2" depending on which devcontainer.json is active/selected.

Note: ${localWorkspaceFolderBasename} returns only the main repository folder name, and ${localWorkspaceFolder} returns the full path up to the main repo folder, so neither reflects the devcontainer subfolder.

Thanks a lot!