Image renderer

[martinRenou]

Fix #253

This only works with JupyterLab 4.1.0 which ships a recent enough version of Lumino.

[martinRenou]

This only works with JupyterLab 4.1.0b1 which ships a recent enough version of Lumino.
We need a strategy for it to fail for older versions.

We cannot fail Python side:

• There is no guaranty the kernel runs in the same environment/machine where JupyterLab runs, so we can't find the JupyterLab version
• There is no guaranty the client is JupyterLab, it could be classic Notebook/VSCode etc.

I decided to fail JavaScript side in the case where the import of ImageRenderer fails:

• This will always work in classic Notebook/VSCode because we ship the right version of Lumino in that case.

[martinRenou]

We can probably wait before merging/releasing this, as JupyterLab 4.1 is not even out yet.

[martinRenou]

Visual regression tests will be fixed by #482