Add deploy app label to toolbar

[nenb]

This PR adds the deploy app label as indicated in the mockups.

I spent some time trying to find a way to dynamically update the label based on whether or not the toolbar was 'narrow'. (I defined narrow as whether or not popupOpener was visible on the toolbar.)

Unfortunately, there appears to be a bug in how the label is set for extensions to the toolbar - it seems to be required to set the label value in the JSON file inside /schema, and the value in index.ts appears to be consistently ignored. See the final comment in https://discourse.jupyter.org/t/jl-4-toolbar-button-with-icon-and-text/20519/2.

I couldn't find a way to update non properties attributes in the JSON file (see also https://github.com/jupyterlab/extension-examples/tree/main/settings) and so I have not included any dynamic update to the label in this PR.

Reference Issues or PRs

#2

What does this implement/fix?

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• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds a feature)
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• Refactoring (no functional changes, no API changes)
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Testing

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[github-actions]

👈 Launch a Binder on branch nebari-dev/jupyterlab-jhub-apps/add-deploy-app-label-toolbar

[nenb]

bot please update snapshots

[krassowski]

Can you use child combinator here? Bare selector on right hand side can impact performance of the entire app. Browser match s lectors right to left traversing entire dom tree (optimizations like bloom filters aside). Adding a more specific rule allows browser to short circuit after looking just at the parent.

[nenb]

Thanks Mike, I didn't appreciate this, really great advice! 🙏

[krassowski]

Thanks @nenb!