Add status bar to map

[gjmooney]

Description

Addresses #306, #316, and maybe #309

Adds a status bar to the map showing a loading indicator, version number, coordinates, and view projection.

I'd appreciate some input on how it looks and which information we want to put on it.

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Checklist

• PR has a descriptive title and content.
• PR description contains references to any issues the PR resolves, e.g. Resolves #XXX.
• PR has one of the labels: documentation, bug, enhancement, feature, maintenance
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📚 Documentation preview: https://jupytergis--348.org.readthedocs.build/en/348/
💡 JupyterLite preview is available from the doc, by clicking on

[github-actions]

👈 Launch a Binder on branch gjmooney/jupytergis/status_bar

[github-actions]

Integration tests report: appsharing.space

[brichet]

This is great, thanks for working on this @gjmooney.

which information we want to put on it.

I don't know how complicated it is, but having it configurable would be wonderful, from the settings or a context menu on the bar itself.

[mfisher87]

This is absolutely beautiful, Greg! I love having the projection info always displayed in the bottom-right like QGIS. What do you think of also including a "scale" indicator on the bar to meaningfully indicate zoom level? Similar to QGIS, expressed as a ratio of 1:n?

[mfisher87]

Huge nitpick: The JGIS version number and the right edge of the loading bar bounce around the slightest bit when the coordinates update.