Make hover tooltip show up automatically after specified delay

[krassowski]

At the moment the user has to press Ctrl (or a different modifier key if changed in settings) to bring up the hover tooltip. We could allow specifying a delay as an alternative/additional activation method. This is how it is implemented in VScode I think.

Sketch for setting schema:

"delay": {
  "title": "Hover delay",
  "type": ["number", "null"],
  "default": 300,
  "description": "Number of milliseconds after which the hover tooltip should be shown. Set to `null` to disable the automatic display of the tooltip (it will still be possible to bring it up with the modifier key)."
},

The following files are relevant:

• packages/jupyterlab-lsp/src/features/hover.ts - for the implementation
• packages/jupyterlab-lsp/schema/hover.json - for schema updates
• atest/05_Features/Hover.robot - for tests

Questions to the users:

• should it be enabled by default?
• what should be the default delay?

[yamaton]

Let's re-ignite this auto-tooltip discussion.

• should it be enabled by default?

Yes. A consistent UI/UX is what I like.

• what should be the default delay?

300 ms, the default value in VS code.

[krassowski]

Closing as this was implemented in #864. Thank you again!