doit tasks about ipyelk

[dfreeman06]

Looks like we need a task to add a symbolic link to the local extension (or I am missing the task where that is currently generated).

[nrbgt]

This is the key task line:

        yield _ok(
            dict(
                name="labext",
                actions=[[*P.APR_DEFAULT, *P.LAB_EXT, "develop", "--overwrite", "."]],
                file_dep=[P.NPM_TGZ, P.OK_PIP_INSTALL],
            ),
            P.OK_LABEXT,
        )

doit setup:labext

By default, it doesn't run that, but rather the "real" install... because I don't think we can release from a "dirty" watch build. I think doit watch does require that file, though, and you run it at the same time as lab (which doesn't care, it's just serving files from $PREFIX/share/jupyter/labextensions).