Implement newUntitled

[martinRenou]

Implement the newUntitled method.

I am reusing the same pattern as the classic JupyterLab file browser where new folders are name Untitled Folder {N} and new files are named untitled{N}.{ext}

[martinRenou]

I see an issue when creating an untitled folder, it gets created properly but JupyterLab seems to be trying to select it in the browser UI before refreshing

[martinRenou]

I see an issue when creating an untitled folder, it gets created properly but JupyterLab seems to be trying to select it in the browser UI before refreshing

This actually was an issue with the get output where the directory name was not right, resulting in JupyterLab trying to select a directory that does not exist.

This should be good to go now!

[jtpio]

Thanks!

[jtpio]

Making a 0.3.0 release with this.