Send a warning if non Python kernel is selected

[pacospace]

Is your feature request related to a problem? Please describe.
As Data Scientist using JupyterLab notebook,

I can use kernels with different programming languages. Currently jupyterlab-requirements support only Python ecosystem.

Describe the solution you'd like
The UI is not started and a dialog warning pops up explaining that the notebook does not uses a Python kernel, therefore the extension cannot be used.

Describe alternatives you've considered

Additional context

[goern]

/kind feature
/priority important-longterm

[sesheta]

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/lifecycle rotten

[sesheta]

Rotten issues close after 30d of inactivity.
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/close

[sesheta]

@sesheta: Closing this issue.

In response to this:

Rotten issues close after 30d of inactivity.
Reopen the issue with /reopen.
Mark the issue as fresh with /remove-lifecycle rotten.

/close

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[sesheta]

Rotten issues close after 30d of inactivity.
Reopen the issue with /reopen.
Mark the issue as fresh with /remove-lifecycle rotten.

/close

[sesheta]

@sesheta: Closing this issue.

In response to this:

Rotten issues close after 30d of inactivity.
Reopen the issue with /reopen.
Mark the issue as fresh with /remove-lifecycle rotten.

/close

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.