Tooltip not showing for Keycaps

[mathematicswizard]

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If the issue has to do with the Compute Engine or MathJSON, please report it
here: https://github.com/cortex-js/compute-engine/issues

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Description

(Optional) Provide a brief summary of the issue.

Adding a tooltip to a keycap doesn't work. It does not show.

Steps to Reproduce

(Required) Provide steps that are specific and repeatable

1. I added the tooltip property to one keycap.
2. I checked a mathfield and it's attached keyboard and the tooltip didn't show.

Actual Behavior

The tooltip didn't show.

Expected Behavior

The tooltip to show when hovering the keycap.

Environment

Is this a regression: did it use to work in a previous version?

I just tested this for the first time and it didn't work.

MathLive version If using the cortexjs.io site, the version is displayed
at the bottom of the page. If using the library, the version is available as
MathfieldElement.version

Using the latest one.

Operating System macOS, Windows, iOS. Include the version

Browser Safari, Chrome, Edge, Firefox, etc... Try several browsers and note
if there are differences between browsers.

Chrome